NRLF 


i 


THE  OCULAR  MUSCLES 


HANSELL  and  REBER 


THE  OCULAR  MUSCLES 


A  PRACTICAL  HANDBOOK  ON  THH  MUSCULAR 
ANOMALIES  OF  THE  EYE 


BY 

HOWARD  P.  HANSELL,  A.  M.,  M.  D. 

PROFESSOR  OF  OPHTHALMOLOGY  IN  THE  JEFFERSON  MEDICAL    COLLEGE;  EMERITUS  PROFESSOR 
OF  DISEASES  OF  THE    EYE,    PHILADELPHIA    POLYCLINIC  AND   COLLEGE    FOR    GRADUATES 
IN      medicine;     OPHTHALMOLOGIST     TO      THE     PHILADELPHIA      GENERAL     HOS- 
PITAL;     MEMBER     AMERICAN     OPHTHALMOLOGICAL     SOCIETY;     FELLOW 
COLLEGE   OF   PHYSICIANS   OF    PHILADELPHIA,  ETC. 

AND 

WENDELL  REBER,  M.  D. 

PROFESSOR     OF     OPHTHALMOLOGY     IN     THE     MEDICAL    DEPARTMENT    OF    TEMPLE    UNIVERSITY; 

PROFESSOR  OF   DISEASES   OF   THE    EYE,    PHILADELPHIA   POLYCLINIC   AND   COLLEGE  FOR 

GRADUATES  IN  MEDICINE;  OPHTHALMOLOGIST  TO  THE  PHILADELPHIA  GENERAL 

HOSPITAL;     CONSULTING    OPHTHALMOLOGIST    TO    THE   RUSH    HOSPITAL 

FOR   CONSUMPTIVES;    MEMBER    OXFORD   OPHTHALMOLOGICAL 

CO!^GRESS;    PAST    PRESIDENT     AMERICAN     ACADEMY     OP 

OPHTHALMOLOGY    AND   OTOLARYNGOLOGY. 


WITH  3  PLATES  AND  82  OTHER  ILLUSTRATIONS 
SECOND  EDITION,  REWRITTEN,  ENLARGED 


PHILADELPHIA 

P.  BLAKISTON'S  SON  &  CO. 

1012  WALNUT  STREET 
1913 


^^' 


Copyright    1912,  by  P.  Blakiston's  Son  &  Co. 


Printed   by 

The  Maple  Press 

)'ork.  Pa, 


PREFACE 


Since  the  authors  presented  their  first  edition  of  a  "Handbook 
on  the  Muscle  Anomahes  of  the  Eye,"  the  interest  in  this  subject 
has  grown  with  the  increasing  demands  and  new  problems  ha\'e 
arisen  which  to-day  demand  solution  and  suggestions  for  their 
practical  relief. 

As  in  the  previous  volume,  the  subject  matter  still  represents 

in  the  main,  the  essence  of  the  lectures  delivered  in  the  regular 

courses  at  the  Philadelphia  Polyclinic.     The  authors  have  again 

sought   "  to   avoid   discussions  and   speculations,   to   emphasize 

methods  that  have  stood  the  test  of  their  own  experience,  and  to 

omit  no  important  data  that  have  been  recognized  as  trustworthy." 

H.  F.  Hansell, 

Wendell  Reber 
Philadelphia,  Pa. 


257864 


CONTENTS 


PART  I. 

ANATOMY  AND  PHYSlOLOCiY. 

Pack 

Anatomy  3 

Physiology      17 

Innervation 17 

Nuclear  Centers 18 

Cortical  Centers ig 

Theory  of  Innervation ig 

General  Considerations 21 

The  Law  of  Direction 22 

Corresponding  Points      23 

Physiologic  Diplopia 24 

Synergistic  Muscles 26 

Associated  Muscles      28 

Antagonistic  Muscles       30 

The  Stcreos(Oi)e 31 

Evolution  of  Binocular  Vision 34 

Tests  for  Binocular  Vision      37 

PART  II. 

STRUCTURAL  ANOMALIES. 

OCUX.A.R  Palsies      43 

Symptomatology       46 

Diagnosis      49 

Special  Paralyses      52 

Prognosis 66 

Treatment 67 

Spasm  of  the  Ocular  Muscles 70 

Nystagmus 70 

PART  III. 

FUNCTIONAL  ANOMALIES. 

Heteroi'horia 75 

General  Considerations 75 

Concerning  Prisms 80 

vii 


Mil  CONTENTS. 

Kflalion  Hctvveen  Accommodation  and  Convergence 82 

Methods  of  Diagnosis 88 

Musrulo-dynamics 98 

Arc  Rotations 109 

Esophoria      114 

Exophoria 126 

Hyperphoria 141 

Dccentering  Lenses 157 

Testing  Prismatic  Lenses 159 

IIeterotropia 163 

Esotropia 165 

Monocular 170 

Alternating 180 

Exotropia       186 

Hypertropia      195 

PART  IV. 
OPERATIONS  ON  THE  MUSCLES. 

Anesthesia      205 

Antisepsis,  Asepsis  and  Instruments      206 

Tenotomy       207 

Advancement  or  Resection 212 

Index:      221 


PART  I. 
ANATOMY  AND  PHYSIOLOGY 


ANATOMY. 


The  voluntary  movements  of  the  eye  are  under  the  control  of 
six  pairs  of  muscles,  six  in  each  orbit.  In  any  and  all  movements 
the  eyes  are  associated  in  their  rotations  and  all  the  muscles  are 
engaged,  some  actively  and  some  passively,  contracting  and  re- 
laxing thus  maintaining  the  balance  or  equipoise  of  the  two 
eyes  necessary  for  binocular  single  vision. 

In  the  study  of  the  functions  of  the  muscles  collectively  and  indi- 
vidually the  orbital  fascia  must  be  considered  (Fig.  i).  Posteriorly 
the  muscles  are  sheathed  in  delicate  transparent  connective  tissue. 


Fig.   I. — Diagrammatic  representation  of  the  relation  of  the  globe  to  the  orbital 
fascia.     (Merkel  and  Kalius.) 

When  they  have  almost  reached  the  eye  ball  the  sheaths  become 
thicker  and  hea\aer.  Anteriorly  the  fascia  divides,  leaves  the 
muscles  and  forms  a  strong  fibrous  sheath  or  cufif  extending  to  the 
orbital  wall  where  it  is  securely  inserted.  It  sends  off  branches 
to  support  the  upper  division  of  the  lacrimal  gland,  to  unite  the 
superior  rectus  with  the  levator  palpebrae  and  the  inferior  rectus 
with  the  tarsus  of  the  lower  lid.  On  the  nasal  side  the  insertion 
of  the  fascia  is  double,  the  upper  part  forming  the  trochlea  and 

3 


ANATOMY   AND    PHYSIOLOGY. 


supporting  the  superior  oblique  after  it  leaves  the  trochlea;  the 
lower  is  bent  backward  and  forms  in  the  vicinity  of  the  posterior 
edge  of  the  nasal  bone  a  wide  insertion  which  reaches  to  the  floor 
of  the  orbit.     The  function  of  the  fascia  is  to  limit  the  efTect  of 


Levator  palpfbrao  super! 


Eyebal' 


Lacrymal  gland 

Inferior  obliquc- 
E.ternal  r< 


Superior  oblique  iendon 
Pulley 


Internal  rectus  i 


-Optic  I 


Superior  oblique  m. 
Levator  patpebrae  superioris  m- 
Superior  rectus  m.  ' 


Fig.  2. — The  orbital  muscles.      (Deaver.) 


muscle  action,  to  hold  the  ball  firmly  in  its  place  in  the  orbit,  and 
to  coordinate  or  balance  associated  contraction  and  relaxation. 

Of  the  six  muscles  in  each  orbit  four  are  straight  and  two 
oblique  (Fig.  2). 


ANATOMY.  5 

The  external  rectus,  supplied  by  the  Oth  nerve,  arises  from 
two  heads — the  larger  from  the  greater  wing  of  the  sphenoid  in 
the  external  and  lower  border  of  the  sphenoidal  fissure;  the  smaller 
from  the  outer  margin  of  the  optic  foramen.  These  two  heads 
soon  become  united  to  form  the  body  of  the  muscle  which  runs 
forward  and  outward,  almost  in  contact  with  the  outer  wall  for 
nearly  half  its  length,  and  loosely  bound  to  it  by  connective  tissue. 
It  is  attached  anteriorly  to  the  sclera  by  a  tendon  3.7  mm.  in 
length,  9.2  mm.  in  width  in  a  convex  line,  the  convexity  toward 
the  cornea,  7  mm.  from  the  outer  limbus.  From  the  tendon  of 
the  external  rectus,  as  from  those  of  all  the  other  muscles, 
adminicula,  or  side  attachments,  are  given  off  to  the  sclera 
which  seem  to  strengthen  the  insertions.  The  area  in  cross 
section  of  its  thickest  portion  equals  16.73  sq-  rnm.  Its  length 
is  45  mm.  (average  for  adults).  The  external  rectus  controls 
the  outer  half  of  the  field  of  fixation  and  rotates  the  cornea  hori- 
zontally temporalward.  It  has  no  action  in  tilting  the  upper 
end  of  the  vertical  meriiand  of  the  cornea  either  inward  or 
outward. 

The  internal  rectus,  supplied  by  the  3d  nerve,  arises  by  a 
tendon  common  to  it  and  to  the  inferior  rectus  from  the  inner 
margin  of  the  optic  foramen,  runs  forward,  lying  close  to  the  inner 
wall  of  the  orbit  and  is  inserted  into  the  sclera  by  an  almost 
vertical  tendon  8.8  mm.  in  length  and  10.3  mm.  in  width,  at 
a  distance  of  6.00  mm.  from  the  inner  limbus.  The  area  of  its 
thickest  portion  is  17.39  sq.  mm.  and  its  length  is  40.8  mm. 
It  controls  the  inner  half  of  the  field  of  fixation,  rotates  the 
cornea  horizontally  nasalward,  and  has  no  torsional  action. 

The  superior  rectus,  supplied  by  the  3d  nerve,  arises  by  a 
tendon  common  to  it  and  to  the  inferior  and  internal  rectus  at 
the  upper  margin  of  the  optic  foramen.  In  its  course  forward  it 
perforates  the  orbital  fat  lying  just  under  and  lightly  connected 
with  the  levator  palpebrae,  curves  round  the  ball,  pierces  the 
layer  of  orbital  fat  and  passes  obliquely  to  its  insertion  into  the 
sclera  anterior  to  the  equator  and  8  mm.  posterior  to  the  corneo- 
scleral border,  bv  a  tendon  5.8  mm.  in  length  and  10.6  mm.  in 


6  ANATOMY   AND    PHYSIOLOGY. 

width.  Its  largest  area  is  ii  1/3  sq.  mm.  and  its  length  41.8  mm. 
From  these  figures  it  will  be  seen  that  the  superior  rectus  is  the 
weakest  of  the  straight  muscles. 

It  controls  the  upper  half  of  the  field  of  fixation,  turning  the 
eye  up,  this  vertical  movement  increasing  as  the  eye  is  abducted 
and  diminishing  as  the  eye  is  adducted;  it  also  rotates  the  cornea 
horizontally  nasal  ward  and  tilts  the  upper  end  of  the  cornea  in, 
more  in  adduction,  less  in  abduction. 

The  inferior  rectus,  supplied  by  the  3d  nerve,  has  the  same 
origin  as  the  internal.  It  lies  close  to  the  floor  of  the  orbit  and  is 
attached  to  the  sclera  by  a  tendon  5.5  mm.  long  and  9.8  mm.  wide, 
at  a  distance  of  7.2  mm.  from  the  limbus.  It  is  indirectly,  by 
means  of  the  lower  orbital  fascia,  connected  with  the  tarsus  of  the 
lower  lid.  Its  largest  area  in  section  is  15.85  sq.  mm.  and  its 
length  is  40  mm.  It  controls  the  lower  half  of  the  field  of  fixation 
turning  the  eye  down,  the  vertical  movement  increasing  with 
abduction,  diminishing  with  adduction.  It  also  turns  the  eye 
laterally  in  and  rotates  the  upper  end  of  the  vertical  meridian  of 
the  cornea  out,  these  effects  increasing  as  the  eye  is  adducted, 
decreasing  as  it  is  abducted. 

The  superior  oblique,  a  long  fusiform  muscle  supplied  by  the 
4th  nerve,  has  its  origin  a  little  above  the  common  origin  of  the 
recti  from  the  lesser  wing  of  the  sphenoid,  passing  forward  and 
upward  to  the  inner  angle  of  the  orbit,  where  as  a  tendon  it  plays 
in,  and  is  supported  by,  a  fibro-cartilaginous  ring  in  the  fossa 
trochlearis.  Upon  resuming  its  course  (the  direction  of  which  is 
now  backward,  downward  and  outward  at  an  angle  of  53°  with 
the  optic  axis),  it  passes  beneath  the  superior  rectus,  to  be  at- 
tached posteriorly  to  the  sclera  midway  between  the  cornea  and 
the  optic  nerve  foramen  16  mm.  from  the  limbus.  The  inser- 
tion forms  nearly  an  antero-posterior  line,  the  large  part  of  the 
tendon  being  attached  posterior  to  the  vertical  equator  of  the 
globe.  The  length  of  the  tendon,  which  commences  before  the 
ring  is  reached  and  is  continued  to  the  scleral  end,  is  19.5  mm., 
and  the  width  of  the  insertion  varies  from  6.8  mm.  to  14  mm. 
It  moves  the  eye  down  and  out  (temporalward)  and  rotates  the 


ANATOMY.  7 

upper  end  of  the  vertical  meridian  inward,  both  movements 
increasing  in  abduction,  diminishing  in  adduction. 

The  inferior  oblique,  supplied  by  the  3d  nerve,  arises  from 
the  anterior  portion  of  the  middle  of  the  floor  of  the  orbit  in  a 
depression  in  the  superior  maxillary  bone  j-ust  external  to  the  an- 
terior end  of  the  lacrimal  groove  and  posterior  to  the  margin  of 
the  orbit.  As  a  thin  narrow  muscle,  it  passes  outward,  backward 
and  upward,  beneath  the  inferior  rectus,  and  is  inserted  by  a 
horizontal  attachment,  about  10  mm.  in  width,  into  the  sclera 
between  the  inferior  and  external  recti  on  the  posterior  hemisphere 
of  the  ball,  17.3  mm.  from  the  limbus.  It  controls  the  upper 
outer  half  of  the  field  of  fixation,  turning  the  eye  upward,  and 
temporalward,  which  effect  increases  in  adduction,  and  diminishes 
in  abduction;^  it  also  turns  the  eye  (laterally)  outward,  more  in 
abduction,  less  in  adduction. 

To  Summarize. — The  insertion  of  the  internal,  inferior, 
external  and  superior  recti  lie,  in  round  numbers,  5,  6,  7,  and  8 
mm.  respectively  from  the  corneal  margin,  forming  what  is  known 
as  the  spiral  of  insertions  (see  Fig.  3).  Naturally,  the  internal 
rectus  has  therefore  the  greatest  mechanica'  advantage  and  the 
inferior  rectus  the  next.  ► 

The  levator  palpebrse,  while  not  strictly  one  of  the  extrinsic 
muscles  of  the  ball,  is  closely  allied,  anatomically  and  pathologic- 
ally, to  them  and  should  be  included  in  a  description  of  the  mus- 
cles of  the  orbit.  It  arises  from  the  under  surface  of  the  lesser 
wing  of  the  sphenoid  above  the  optic  foramen,  passes  forward 
above  and  in  close  juxtaposition  to  the  superior  rectus  in  the  first 
half  of  its  course,  and  is  inserted  into  the  upper  edge  of  the  tarsal 
cartilage  by  an  aponeurosis  as  broad  as  the  cartilage.     These  two 

'  Volkman's  results  of  measurement  of  movements,  quoted  by  Weiland,  Archives 
of  Ophthal.,  January,  1898,  are: 

Rect.  Ext.  moves  eyeball  out,  up;  rotates  upper  cornea  inward. 
Rect.  Int.  moves  eyeball  in,  up;  rotates  upper  cornea  outward. 
Rect.  Sup.  moves  eyeball  up,  in;  rotates  upper  cornea  inward. 
Rect.  Inf.  moves  eyeball  down,  in;  rotates  upper  cornea  outward. 
Obi.  Sup.  moves  eyeball  down,  out;  rotates  upper  cornea  inward. 
Obi.  Inf.  moves  eyeball  up,  in;  rotates  upper  cornea  outward. 


8  ANATOMY   AND    PHYSIOLOGY. 

muscles  are  so  intimately  associated  in  their  location  and  course- 
that  contraction  of  one  involves  partial  contraction  at  least  of  the 
other. 

Capsule  of  Tenon. — The  fascias  of  the  muscles  are  not  so 
distinctly  separated  from  each  other  that  they  may  be  individu- 
ally described,  for  they  are  closely  interwoven  with  themselves  and 
with  the  connective  tissue  leaves  which  bind  together  the  orbital 
fat. 

The  ball  itself  is  surrounded  by  a  thin,  relatively  strong  con- 
nective tissue  capsule  (Tenon's)  lined  with  endothelium  which  is 

SUP.  RECTUS. 
'  8mm. 


6  m  ni  ■ 
/  A/ f.  RECTUS. 

Fig.  3. — The  spiral  of  insertions. 


developed  out  of  the  sheets  in  the  fat  behind  the  orbit  and  is  di- 
rectly connected  with  them.  It  is  connected  every  where  with  the 
ball  by  tender  connective  tissue  bundles.  It  takes  the  place  of 
the  bony  walls  in  the  movement  of  the  eyeball  as  in  a  ball  and 
socket  joint.  Instead  of  the  synovial  space  found  in  joints,  the 
capsule  of  Tenon  is  here  pierced  by  connective  tissue  bundles.  It 
is  said  by  Schwalbe  to  be  a  lymph  space — (Tenon's  space) — 
which  is  denied,  however,  by  Langer,  who  says  it  never  contains 
lymph  nor  is  it  connected  with  the  lymph  spaces  of  the  eye.  The 
"adminicula"  (side  attachments)  of  the  muscles  already  described 


ANATOMY.  9 

are  to  be  considered  as  collections  of  these  connective-tissue 
bundles.  Through  a  small  opening  in  the  capsule,  the  latter  may 
be  blown  up  easily.  Tt  ends  a  short  distance  behind  the  cornea, 
having  amalgamated  with  the  conjunctiva.  Posteriorly  it  ends  in 
an  irregular  line  surrounding  the  ciliary  nerves  and  blood-vessels 
and  forming  a  ring,  i  cm.  in  diameter  through  which  the  optic 
nerve  passes.  There  are  two  layers  to  the  capsule — one  lying 
very  close  to  the  eyeball,  the  other  surrounding  it  more  or  less 
loosely.  The  muscular  tendons  break  through  the  capsule  in 
slits  and  are  connected  with  its  edges  by  connective  tissue. 

The  muscles  are  covered  by  delicate  connective  tissue  about 
one-half  way  to  the  ball,  then  the  sheath  becomes  heavier.  This 
heavy  fascia  does  not  accompany  the  tendons  through  their  slits 
in  Tenon's  Capsule,  but  bends  away  inward  and  outward.  On 
that  side  toward  the  ball  it  amalgamates  with  the  capsule  and 
strengthens  the  above  described  strong  connective-tissue  ring. 
The  outer  half  of  the  fascia  becomes  much  thicker  and  gives  off 
branches  and  sheaths  which  bend  sideways  and  attach  themselves 
firmly  to  the  bone.  There  are  three  such  insertions.  On  the  up- 
per temporal  aspect  the  fascia  from  three  muscles  collects.  The 
insertion  is  so  placed  that  it  supports  the  upper  lacrimal  gland. 
From  it  are  given  off  the  connective-tissue  sheaths  of  the  levator 
palpebrse  and  the  superior  rectus  and  the  (from  below)  external 
rectus.  On  the  nasal  side  the  insertion  is  double,  upper  and  lower, 
the  upper  to  the  superior  oblique;  the  lower  is  bent  back  and  forms 
in  the  vicinity  of  the  posterior  edge  of  the  nasal  bone  a  wide, 
downward  inclining  line  which  begins  at  the  inner  canthus  and 
reaches  to  the  floor  of  the  orbit. 

Differences  of  opinion  prevail  as  to  the  function  of  Tenon's 
capsule.  It  was  long  believed  and  still  is  held  by  many  authorities 
that  the  two  layers  of  the  capsule  enclose  a  lymph  space  connected 
by  lymph  vessels  with  the  suprachoroidal  space,  and  thus  form  an 
important  link  in  the  chain  of  lymph  spaces  w^hich  connect  the 
eye  with  the  intracranial  lymph  system.  Leber  (Graefe  Saemisch) 
on  the  other  hand,  asserts  that  it  is  not  a  lymph  space,  nor  is  it 
connected    with  the  lymph  spaces  of  the  eye.     Its  function  is 


lO 


ANATOMY  AND    PHYSIOLOGY. 


somewhat  like  that  of  a  synovial  membrane  and  permits  the  ocu- 
lar movements  without  friction. 

Check  Ligaments. — In  operations  on  the  muscles,  the  prolonga- 
tions of  the  enveloping  sheaths  of  fascia  must  not  be  disregarded. 
Difficulty  in  picking  up  the  tendons  with  the  strabismus  hook  is 
often  encountered,  because  the  incision  has  failed  to  divide  both 
layers  of  the  capsule,  and  the  effect  desired  of  a  tenotomy  is  not 
secured,  because  attention  has  not  been  given  to  the  radical 
supporting  attachments  derived  from  the  capsule  and  the  check 
ligaments  which  are  a  portion  of  the  orbital  fascias.     Serious  in- 


FiG.  4. — The  internal 
check  hgament  (a)  serves 
to  prevent  excessive  ac- 
tion of  the  external  rectus 
after  extensive  tenotomy 
of  the  internus. 


Fig.  5. — The  internal 
check  hgament  (a)  being 
put  upon  the  stretch  by 
the  contracted  internal 
rectus. 


Fig.  6. — ^Diagram  of 
the  check  Ugaments.  a, 
internal  check  hgament; 
b,  external  check  Hga- 
ment. 


fiammation  (tenonitis),  with  extension  of  the  inflammatory  pro- 
cess backward,  may  result  from  traumatism  to  this  serous 
envelope  (Fig.  4). 

These  condensations  of  connective  tissue  which  are  more  or  less 
gathered  together  opposite  the  four  recti  muscles  and  are  known 
as  the  check  ligaments  are  not  necessarily  as  sharply  limited  as 
they  are  shown  in  Fig.  4  and  yet  they  bear  a  distinct  relation  to  the 
neighboring  muscles  and  they  are  therefore  today  recognized  under 
the  above  name.  Ordinarily  no  force  is  exerted  by  them,  but  when 
for  instance  the  interni  are  under  forced  action  as  shown  in  Fig. 
5  the  internal  check  ligaments  serve  to  prevent  exaggerated 
action  on  the  part  of  the  interni  muscles  while  the  external  check 
ligaments  are  relaxed.     Moreover,  after  extensive  tenotomy  of 


ANATOMY. 


II 


the  internal  rectus,  the  corresponding  check  ligament  is  put  upon 
more  or  less  constant  stretch  and  may  e\'en  limit  the  action  of  the 
eyeball  somewhat  (Fig.  6). 


Ofb:;i 

I  fascu 

Capule  of  Tenon          ( 

fM 

Sufx-rioj  r»ttus  m'. 

LayMor  palpebrji 

1 

9up«rioris  m. 

[ 

Coinection  b..;wcen  superior  rcclu;  m. 
and  levator  pjlpcbro)  tup«rioii(  m 

Capsule  of  Tenon 

Fornix  conjunctiva 

Suptuip  Orbitil.^  0 
I     orblto-tarsal  lii 


Supravaginal  lymph  rp  • . 
Fikfous  shelih  u(  ui<t>c  n 
Iniervaginal  lymph  sp  ; 

Pe'iosieum  of  orbit  i 
Optic  n. 


\    Capsule  of  Tenon 
Check  lig  of  inferior  rectus  m. 

inferior  .oblique  m 
OrbiUl  fascia 


Capsunof  Tenon 


Fig.  7. — Tenon's  capsule  and  orbilal  fascias.     (Deaver.) 

The  space  between  the  ball  and  the  orbital  walls,  not  occupied 
by  muscles  and  nerves,  is  filled  with  fat  in  great  part,  and  by  con- 


12 


ANATOMY   AND    PHYSIOLOGY. 


nectivc  tissue.  The  connective  tissue  of  the  orbit  is  so  arranged 
as  to  form  light  fibrous  bands,  probably  containing  elastic  tissue, 
supporting  and  steadying  the  muscles  during  action  and  maintain- 
ing the  suspension  of  the  ball  (Fig.  7). 

The  functions  of  the  fascia  are  limitation  of  muscle  effect;  to 
hold  the  eyeball  firmly  in  its  position,  to  guard  the  conjunctiva  in 
movements  of  the  globe  and  to  associate  the  action  of  the  su- 
perior rectus  and  the  upper  lid,  and  the  inferior  rectus  and  the 
lower  lid. 

NERVE  SUPPLY  OF  THE  INDIVIDUAL  MUSCLES. 
The  3d.  4th,  and  6th  cranial  nerves,  known  as  the  oculomotor, 
pathetic  and  abducens  nerves,  together  supply  the  external  ocular 


P"lG.  8. — Nerves  of  the  orbit.      (Dearer.) 

muscles  (Fig.  8).  The  3d  nerve  also  gives  off  a  branch  to  the  oph- 
thalmic or  lenticular  ganglion,  forming  its  motor  root  to  the  inte- 
rior ocular  muscles.     The  scheme  or  hypothesis  which  explains  the 


ANATOMY. 


13 


largest  number  of  3d  ner\e  nuclear  problems  is,  probably,  that 
of  Bernheimer'  (Fig.  9). 

The  vascular  supply  is  shown  in  Fig.  10. 

As  the  libers  of  the  third  nerve  leave  the  mass  of  gray  substance 
which  lays  along  each  side  of  the  median  line,  in  the  anterior 
part  of  the  fourth  ventricle,  they  converge  as  they  pass  downward 
to  pierce  the  dura  mater  below  the  posterior  clinoid  process; 
the  nerve-trunk  there  passes  along  the  outer  wall  of  the  cavern- 


Fic;.  Q. — Schematic  projection  of  the  nucleus  of  the  third  and  fourth  nerves  in  the 
floor  of  the  fourth  ventricle,  a  and  b,  nucleoli  for  the  intraocular  muscles  (iris  and 
ciliary  muscle) ;  c,  levator  nucleolus;  d,  superior  rectus  nucleolus;  e,  internal  rectus 
nucleolus;  /,  inferior  oblique  nucleolus;  g,  inferior  rectus  nucleolus;  h,  fourth  nerve 
nucleus  or  superior  oblique  nucleus.  (Bernheimer,  Graefe-Saemisch  Handbuch, 
second  edition.) 


ous  sinus,  enters  the  orbit  through  the  sphenoid  fissure  and  divides 
into  two  branches.  The  superior  division  supplies  the  superior 
rectus  and  levator  palpebrae;  the  inferior  division  separates  into 
three  branches,  one  going  to  the  internal  rectus;  and  the  third, 
and  largest,  to  the  inferior  oblique;  and  one  to  the  inferior  rectus. 
A  fourth  goes  to  the  short  root  of  the  lenticular  ganglion.  From 
the  lenticular  ganglion  are  given  off  the  long  ciliary  ner\es  which 

'  Some  authorities  prefer  Perlia's;  others  Kahler  &  Pick. 


14 


ANATOMY   AND    PHYSIOLOGY. 


perforate  the  sclera  around  the  optic  nerve,  pass  forward  between 
the  sclera  and  choroid  and  are  distributed  to  the  iris  and  ciliary 
muscle.  The  terminal  branches  anastomose  finally  with  the 
terminals  of  the  seventh.  The  nerve-trunk  also  receives  fila- 
ments from  the  cavernous  plexus  of  the  sympathetic,  and  its 
superior  division  is  not  infrequently  connected  with  the  ganglionic 
branch  of  the  nasal  nerve. 


Fig.  io. — Vascular  supply  to  the  oculomotor  nuclei,  a,  Roof  of  the  corpora 
quadrigemina;  b,  acqueduct  of  Sylvius;  c,  sphincter-iridis  and  ciliary  muscle  nucleus; 
d,  f,  and  g,  vascular  supply  to  the  remaining  nuclei.  (Bernheimer,  Graefe- 
Saemisch  Handbuch,  second  edition.) 


The  4th,  pathetic  or  trochlear  nerve  supplies  the  superior 
oblique  muscle.  Its  deep  origin  can  be  traced  to  the  nucleus 
which  lies  beneath  the  aqueduct  of  Sylvius,  behind  and  on  a 
lower  level  than  the  third  nerve  nucleus.  The  fibers  pass  as  they 
emerge  to  the  dorsal  aspect  of  the  aqueduct  and  decussate  with 
the  fibers  of  the  opposite  side  ?) .  The  nerve-trunk  pierces  the 
dura  mater  near  the  posterior  clinoid  process,  passes  with  the 
3d  nerve  along  the  outer  wall  of  the  cavernous  sinus  and  enters 


ANATOMY.  15 

the  orbit  through  the  sphenoidal  fissure,  being  the  highest  of 
the  nerves  passing  through  the  orbit.  It  also  receives  filaments 
from  the  cavernous  plexus  of  the  sympathetic,  and  transmits  a 
twig  to  the  lacrimal. 

The  nucleus  of  the  6th  or  abducens  nerve  consists  of  multiple 
ganglion  cells  lying  immediately  under  the  center  of  the  floor  of 
the  4th  ventricle  on  either  side  of  the  median  sulcus.  It  is  bor- 
dered on  its  inferior,  inner  and  upper  sides  by  the  first,  second 
and  third  portions  of  the  facial  nerve.  The  fibers  run  obliquely 
downward  to  emerge  at  the  lower  border  of  the  pons.  The 
connections  of  the  6th  nerve  nucleus  are  said  by  Bruce  {loc.  cit.) 
to  be  as  follows:  with  the  second  part  of  the  root  of  the  facial 
nerve  and  the  segment  of  the  3d  nerve  nucleus  supplying  the 
internal  rectus;  with  the  auditory  nucleus  and  with  the  cortex  of 
the  opposite  cerebral  hemisphere,  and  perhaps  with  that  of  the 
same  side.  The  nerve  penetrates  the  dura  mater  on  the  basilar 
surface  of  the  sphenoid  bone,  passes  through  the  posterior  or 
clinoid  processes,  enters  the  cavernous  sinus,  and  finally  the  orbit 
through  the  sphenoidal  fissure,  to  be  distributed  to  the  external 
rectus  muscle  from  its  inner  surface.  It  also  receives  filaments 
from  the  carotid  and  cavernous  plexus  of  the  sympathetic  nerve, 
from  Meckel's  ganglion  and  from  the  ophthalmic  nerve. 

VASCULAR  SUPPLY. 

The  vascular  supply  to  the  muscles  is  derived  from  the  muscular 
branches  of  the  ophthalmic  artery,  one  of  the  terminal  branches 
of  the  internal  carotid. 

The  ophthalmic  artery  at  its  origin  is  2  mm.  in  diameter.  It 
passes  through  the  optic  foramen  under  the  optic  nerve,  supplying 
its  sheaths  and  perineurium,  later  perforating  and  supplying  the 
nerve-substance  itself.  Soon  after  its  entrance  into  the  orbit,  it 
gives  oft'  the  muscular  branches.  All  the  blood-vessels  of  the 
orbit  are  characterized  by  their  tortuous  course  and  their  lax 
attachments  to  flexible  structures.  They  are  thus  enabled  to 
accompany  the  movements  of  the  ball  without  tearing. 

The  muscular  arteries  are  two  in  number,  the  smaller  passing 


l6  '  ANATOMY   AND    PHYSIOLOGY. 

up  and  medianward,  the  larger  downward  and  laterally,  supply- 
ing the  muscles  in  their  course.  They  give  off  the  anterior 
ciliary  branches  which  perforate  the  tendons  of  the  muscles  and 
the  sclera,  and  supply  the  ciliary  region  and  iris  with  blood. 
(Section  of  one  of  these  arteries  in  tenotomy  often  gives  rise  to 
profuse,  but  never  alarming  hemorrhage.) 

The  arteries  are  accompanied  by  veins  situated  similarly  and 
described  under  similar  names. 

The  most  important  orbital  vein  is  the  superior  ophthalmic, 
with  which  all  venous  branches  in  the  orbit  are  in  direct  or  in- 
direct connection.  It  collects  blood  from  the  frontal,  nasal, 
supra-orbital,  angular,  venae  vorticosse,  and  the  central  retinal 
veins.  Its  course  is  along  the  superior  rectus,  backward  in  the 
muscular  cone,  emptying  into  the  cavernous  sinus. 


PHYSIOLOGY. 

INNERVATION. 

The  muscles  governing  the  movements  of  the  eyeball,  the  ac- 
commodation and  the  iris  are  innervated  by  the  3d,  4th  and  6th 
pair  of  cranial  nerves  and  the  carotid  plexus  of  the  sympathetic 
system.  The  former  have  their  deep  origin  in  the  posterior  ex- 
tremity of  the  aqueduct  of  Sylvius  and  the  anterior  part  of  the 
floor  of  the  4th  ventricle.  The  muscular  movements  are  volun- 
tary because  they  are  represented  by  distinct  areas  in  the  cor- 
tex. From  these  cortical  centers  are  derived  nerve  fibers 
which  run  indirectly  to  the  nuclei  and  undoubtedly  have  con- 
nections with  other  centers  in  the  brain,  the  functions  of  which 
are  associated.  The  fibers  have  not  been  dissected  or  strictly 
outlined.  Their  presence  must  be  assumed  in  the  explanation 
of  mental  processes,  part  of  the  evidence  of  which  are  the 
voluntary,  although  not  always  conscious,  ocular  movements. 
The  nuclei  on  the  other  hand  have  been  studied,  their  exact 
location,  their  relations  to  each  other  and  their  functions  to  a  large 
extent  determined.  From  the  nuclei  large  numbers  of  nerve 
fibers  are  given  off  which  immediately  unite  to  become  distinct 
nerve  trunks  easily  seen  at  the  base  of  the  brain  and  followed 
to  their  exit  through  the  sphenoidal  fissure  to  be  distributed  to 
their  respective  terminations  in  the  muscular  tissues  and  probably 
anastomosing  with  the  terminal  branches  of  the  7th  nerve. 

Russell's  experiments  have  led  him  to  conclude  that  the  cere- 
bellar cortex  plays  no  little  part  in  ocular  movements  and  that 
it  is  associated  with  the  cerebrum  in  these  functions.  The  ac- 
companying drawing,  Fig.  11,  based  on  Russell's  experiments, 
indicate  the  areas  which  are  supposed  to  preside  over  the  different 
eye  movements.  It  will  be  observed  that  they  are  above  the 
center  of  the  fissure  of  Syhius  just  anterior  to  the  large  motor 
2  17 


15  ANATOMY  AND   PHYSIOLOGY. 

area,  and,  moreover,  that  they  are  close  to  the  facial  area,  and 
on  the  left  side. 

NUCLEAR  CENTERS. 

The  mass  of  cells  composing  the  nucleus  of  the  3d  lies  on  both 
sides  of  the  median  line  next  to  the  corpora  quadrigemina  and 
under  the  aqueduct  of  Syhius  anterior  to  and  on  the  floor  of  the 
4th  ventricle.  The  nucleus  is  from  6  to  10  mm.  in  length 
and  of  varying  breadth  mingling  imperceptibly  with  adjacent 
cells.     Posteriorly   they   encroach    upon    the   cells   of    the   4th 


Fig.  II. — The  external  surface  of  the  right  half  of  the  brain  of  the  ape  (Macacus 
Sinicus).  (After  Russell,  Journal  of  Physiology,  vol.  17,  p.  8.)  i,  Upward  move- 
ment of  both  eyes;  2,  downward  movement  of  both  eyes;  3,  movement  of  both  eyes 
upward  and  to  the  opposite  side;  4,  movement  of  both  eyes  downward  and  to  the 
opposite  side;  5,  convergence.  The  numbers  denote  the  chief  foci,  excitation  of 
which  evoked  movements  of  the  eyes  other  than  conjugate  turning  to  the  opposite 
side  from  the  hemisphere  stimulated. 

nucleus  w^ithout  a  distinct  line  of  demarkation  between  them. 
The  mass  may  be  divided  into  nucleoli  each  with  its  separate 
function  and  muscle  control.  In  the  accompanying  diagram  the 
anatomy  and  physiology  is  schematically  shown. 

It  will  be  noticed  that  from  some  of  the  nuclei  the  fibers  run 
direct  to  the  muscles  on  the  same  side,  while  others  are  crossed  to 
stimulate  those  on  the  other  side,  the  crossing  taking  place 
mostly  in  the  anterior  half  of  the  nucleus.  Speaking  generally 
the  inner  or  median  part  of  the  nucleus  belongs  to  the  intraocular 
muscles  and  the  outer  portions  to  the  extra-ocular  muscles.     The 


PHYSIOLOGY.  19 

anterior  and  ])rinci])al  part  of  the  nuclear  masses  belongs  to  the 
3d  nerve.  Adjoining  the  proximal  or  posterior  end  of  the 
posterior  corpora  quadrigemina  on  both  sides  are  the  nuclei, 
right  and  left,  of  the  trochlearis.  Much  farther  back  and  in 
juxtaposition  with  the  facial  muscles  and  fibers  is  the  nucleus  of 
the  abducens. 

CORTICAL  CENTERS. 

Having  conducted  a  large  number  of  experiments  on  monkeys 
to  determine  the  site  of  the  centers  for  eye  movements,  St.  Bern- 
heimer  (Graefe  Saemisch,  second  edition)  has  reached  the  follow- 
ing conclusions :  i.  The  gyrus  angularis  and  especially  its  middle 
part  of  both  hemispheres  is  the  only  cortical  center  for  synergic 
eye  movements.  2.  The  right  gyrus  angularis  controls  move- 
ments toward  the  left,  up  and  left,  and  down,  the  left  gyrus 
controls  movements  toward  the  right,  up  and  right,  and  down. 
3.  The  anterior  corpora  quadrigemina  are  neither  a  reflex  center 
for  eye  movements  nor  the  passage  for  the  neurons.  4.  Since 
after  median  section  of  the  brain  between  the  aqueduct  of  Syhius 
and  the  nuclei  region  of  the  eye  muscles  irritation  of  both  angular 
gyri  produces  no  eye  movement,  therefore  the  connection-neurons 
between  the  nuclei  and  the  cortex  are  all  crossed  in  the  angular 
gyrus  in  the  median  line  under  the  plane  of  the  aqueduct  of  Sylvius 
between  it  and  the  nuclei.  5.  The  end  filaments  of  the  con- 
necting fibers  communicate  probably  by  other  cells  (schalzellcn) 
with  the  roots  of  the  motor  ganglion  cells  of  the  nuclei.  6.  The 
schalzellen  lie  probably  imbedded  and  scattered  in  the  central 
gray  matter  and  form  no  cell  mass.  7.  In  consequence  of  partial 
crossing  of  the  3d,  the  total  crossing  of  the  4th,  and  the  con- 
nection of  all  the  oculomotor  nuclei  with  each  other,  it  may 
well  be  asked  whether  the  crossing  connecting  fibers  of  one  angu- 
lar gyrus  equally  influence  the  muscles  of  both  eyes  ? 

THEORY  OF  INNERVATION. 

To  outline  the  structure  and  function  of  each  of  the  individual 
eye-muscles  is  a  relatively  simple  matter,  yet  it  is  by  no  means  so 


20  ANATOMY   AND    PHYSIOLOGY. 

easy  a  task  to  give  a  satisfactory  explanation  of  the  innervational 
state  of  the  eye-muscles  corresponding  to  all  the  positions  the  eyes 
may  assume  in  monocular  or  binocular  fixation.  The  theory  that 
has  gained  the  widest  acceptance  is  the  so-called  innervational 
theory,  so  ably  championed  by  Hansen  Grut,  1898.  It  ])rovides 
that  every  contraction  of  a  muscle  or  set  of  muscles  to  produce  oc- 
ular movement  in  a  given  direction  is  accompanied  by  relaxation 
of  the  muscle  or  set  of  muscles  that  are  directly  antagonistic  to 
the  contracting  muscles,  which  relaxation  keeps  even  pace  with 
the  contraction  going  on  in  the  muscles  producing  the  deviation. 
As  the  eyes  are  capable  of  being  easily  rotated  there  must,  in 
order  that  single  vision  be  preserved,  be  a  balance  among  the 
forces  that  tend  to  move  the  eyes  in  various  directions.  This 
balance  is  possible  only  under  two  conditions:  i,  that  all  the 
muscles  be  slack  and  exert  no  tension  (an  untenable  hypothesis) ; 
or  2,  that  all  the  muscles  so  tend  to  contract  as  to  cause  an  equal 
rotational  strain  in  all  directions.  Hence,  we  suppose  that  the 
muscles  are  always  in  a  state  of  partial  tonic  contraction,  at  any 
rate  during  the  period  of  full  consciousness. 

There  is  no  limitation  to  the  directions  in  which  the  eye  can 
be  rotated  by  the  action  of  one  or  more  muscles,  and  under  certain 
circumstances  a  contraction  of  all  the  muscles  produces  a  slight 
enophthalmus. 

The  primary  position  of  the  eyes  is  observed  when  an  individual 
holds  the  head  erect  and  gazes  straight  in  front  toward  infinity  in 
the  horizontal  plane  of  the  eyes. 

The  predominately  active  muscles  in  the  following  movements 
from  the  primary  position  are: 

Right  and  left  turning;  only  the  rectus  externus  and  rectus  inlernus. 

Upward  turning;  rectus  superior  and  inferior  oblique. 

Downward  turning ;  rectus  inferior  and  superior  oblique. 

Up  and  out  turning;  rectus  superior,  inferior  oblique,  and  rectus  externus. 

Down  and  out  turning;  rectus  externus,  rectus  inferior  and  superior  oblique. 

Down  and  in  turning;  rectus  internus,  rectus  inferior,  and  superior  oblique. 

Up  and  in  turning;  rectus  internus,  rectus  superior  and  superior  oblique. 

These  are  the  eight  principal  secondary  positions,  and  in  all 
the  degrees  of  the  circle  between  them  the  rotation  will  be  accom- 


PHYSIOLOGY.  21 

plishcd  by  the  combined  action  of  the  muscles  normally  turning 
the  cornea  to  these  positions.  The  extent  of  the  turnings  in  the 
field  of  fixation  varies,  according  to  different  observers.  The 
average  is  probably  as  follows : 

up       up-out       up-in        out        in       down    down-out      down-in 
40-50    35-50       40-55     35-55  40-4S  40-70       35-60  25-60       (Diiane). 

The  discrepancies  arise  from  variations  in  the  normal  power  of 
the  muscles  of  one  individual  as  compared  with  another,  and  the 
degree  of  attention  and  effort  of  which  an  individual  is  capable. 
Also,  in  determining  the  rotation  by  Stevens's  tropometer,  the 
form  of  the  ball  must  be  taken  into  consideration.  Such  wide 
variations,  as  the  averages  given  above,  are  confusing  to  one 
who  endeavors  to  determine  whether  a  certain  movement  is 
normal  or  otherwise. 

GENERAL   PHYSIOLOGIC  CONSIDERATIONS. 

The  Law  of  Projection.—  To  properly  understand  the  phe- 
nomena of  \ision,  certain  peculiar  functions  of  the  retina,  optic 
nerve,  and  associated  brain  apparatus  must  be  clearly  appre- 
hended, for  they  lie  at  the  very  basis  of  these  phenomena. 

While  it  is  true  that  images  are  formed  on  the  retina,  we  do  not 
actually  see  the  retinal  images.  In  fact,  we  do  not  actually  see 
anything  in  the  eye  but  something  outside  in  space.  The  retinal 
image  is  conveyed  by  way  of  the  optic  nerves  and  tracts  to  the 
brain,  there  to  determine  certain  changes.  These  changes  or 
ejects  the  brain  then  refers  or  projects  outward  in  a  definite  direc- 
tion into  space  as  an  external  image  or  facsimile  of  the  object  which 
produces  it.  So  that  what  we  see  as  external  images  are  really 
projections  outward  of  retinal  images.  This  law  of  outward 
projection  is  important.  It  is  not  a  new  law,  specially  made  for 
the  sense  of  sight,  but  only  a  modification  of  a  general  law  of 
sensation.  This  general  law  is  that  irritation  or  stimulation  in 
any  portion  of  a  sensory  fiber  is  referred  to  its  peripheral  ex- 
tremity. If  the  ulnar  nerve  is  pinched  in  the  hollow  on  the  inner 
side  of  the  point  of  the  elbow,  pain  is  felt  in  the  little  and  ring 


22 


ANATOMY   AND    PHYSIOLOGY. 


fingers,  where  this  nerve  is  distributed.  In  the  case  of  the  optic 
nerve  the  impression  is  so  wholly  projected  outward  that  we  arc 
unconscious  of  any  sensation  in  the  eye  at  all.  Hence  what  we 
are  accustomed  to  call  the  field  of  view  is  nothing  else  than  the 
external  projection  into  space  of  various  retinal  stimulations. 

The  Law  of  Direction. — The  direction  of  external  projection 
may  be  exactly  (or  nearly  exactly)  defined  as  follows: 

The  central  ray  of  each  point  in  the  field  of  view  passes  straight 
through  the  nodal  point  of  the  lens  without  de\dation  to  the  retina. 

It  is  evident  then  that  every  retinal 
rod  and  cone  has  its  inevitable 
related  point  or  spot  in  the  field  of 
view  (visual  field)  and  vice  versa. 
The  two  points — retinal  and  spatial 
— exchange  with  one  another  by 
impression  and  outward  projection 
along  the  straight  lines  connecting 
them.  This  is  represented  in  Fig. 
12  in  which  S  S  represents  the 
spatial  concave  and  R  R  the  retinal 
expanse,  with  straight  lines  of  rays 
of  light  connecting.  A  ray  from  a 
point  c  in  space  passes  in  a  straight 
line  through  the  nodal  point  of  the 
lens  w,  and  strikes  a  certain  retinal 
rod  c;  that  impression  is  projected 
by  the  rod  (or  referred  by  the  brain)  back  along  the  ray  line 
to  the  place  whence  it  came.  Study  of  the  figure  shows  that 
the  position  of  all  retinal  images  must  be  the  reverse  of  the 
objects  in  space — that  the  upper  part  of  the  field  of  view  corre- 
sponds to  the  lower  part  of  the  retina  and  the  lower  part  of  the  field 
of  view  (visual  field)  to  the  upper  part  of  the  retina.  Similarly 
the  right  and  left  sides  of  the  visual  field  are  related  to  the  left 
and  right  sides  respectively  of  the  retina. 

These  two  laws — the  law  of  external  projection  and  the  law 
of  direction — are  two  of  the  most  fundamental  laws  of  vision. 


Fig.  12. — Scheme  of  the  law  of 
direction.  The  larger  circle  repre- 
sents the  limits  of  space;  the 
smaller  one  the  retina. 


PHYSIOLOGY.  23 

The  first  shows  why  objects  are  seen  externally  in  space;  the 
second  gives  the  exact  place  where  they  are  seen,  that  is  to  say 
where  the  brain  locates  them.  The  general  law  of  projection  is 
not  followed  \ery  exactly  with  respect  to  the  very  forwardmost 
portions  of  the  retina  in  the  region  of  the  ora  serrata. 

What  has  been  thus  far  said  treats  only  of  the  phenomena 
of  monocular  \ision.  But  most  individuals  possess  two  eyes, 
and  these  are  not  to  be  considered  as  mere  duplicates  so  that  if  we 
lose  one  we  still  have  another.  Quite  on  the  contrary,  the  two 
eyes  ordinarily  act  together  as  one  instrument.  There  are  many 
visual  phenomena  and  many  judgments  based  upon  these  phe- 
nomena which  result  entirely  from  the  use  of  two  eyes  as  one  in- 
strument. The  phenomena  of  binocular  vision  are  far  less  purely 
physical  than  those  of  monocular  vision.  They  are  also  more 
obscure,  illusory  and  difficult  of  analysis  because  more  subjective 
and  more  closely  allied  to  psychical  phenomena. 

Corresponding  or  Identical  Points. 

As  is  well  known,  the  retinas  are  two  deeply  cup-shaped  ex- 
pansions of  the  optic  nerve.  R  and  L  (Fig.  13)  represent  a  fiat 
(or  Mercator)  projection  of  these  two  cups.     The  black  spots  in 


Fig.  13. — Mercator  projection  of  the  two  retinas;  showing  corresponding  retinal 

points. 

the  centers  represent  the  central  spots.  If  now  we  draw  vertical 
lines  (vertical  meridians)  A,  B,A',  B',  through  the  central  spots 
and  divide  the  retinas  into  equal  halves,  then  the  left  or  shaded 
halves  would  correspond  point  for  point;  i.e.,  the  internal  or  nasal 


24  ANATOMY  AND   PHYSIOLOGY. 

half  of  one  retina  corresponds  with  the  external  or  temporal 
half  of  the  other  and  vice  versa.  More  accurately  if  the  concave 
retinas  be  divided  by  coordinates  like  the  lines  of  latitude  and 
longitude  of  a  globe  (ab,  and  xy  being  the  meridian  and  equator), 
then  points  of  similar  longitude  and  latitude  in  the  two  retinas, 
as  D,D',  and  E,E/  are  corresponding  points.  Of  course  the  cen- 
tral spots  will  be  corresponding  points;  also  points  on  the  vertical 
meridians,  A,A',  B,B',  at  equsd  distances  from  the  central  spots 
will  also  correspond.  ^  These  phenomena  therefore  afford  the  basis 
for  the  following: 

Law  of  Corresponding  or  Identical  Retinal  Points. — Ob- 
jects are  seen  single  when  their  retinal  images  Jail  on  corresponding 
or  identical  retinal  points. 

Of  course  it  is  true  that  as  there  are  two  retinas  there  are  natu- 
rally two  retinal  images  of  every  external  object,  and  since,  as 
has  been  shown,  retinal  images  are  projected  outward  into  space 
as  external  images,  one  will  certainly  have  two  external  images 
of  every  object.  If  then  there  are  two  external  images  for  every 
object,  it  may  be  asked  why  are  not  all  objects  seen  double? 
And  it  may  be  answered  that  all  objects  are  indeed  seen 
double  except  under  certain  conditiois. 

PHYSIOLOGIC  DIPLOPIA. 

The  phenomena  of  double  images  of  all  objects  except  under 
certain  conditions  is  a  fundamental  one  in  binocular  vision,  yet 
it  is  commonly  overlooked  by  even  the  most  intelligent  persons 
unaccustomed  to  analyzing  their  visual  impressions.  If  one 
holds  up  one's  index  finger  at  arm's  length  and  then  looks  not  at 
the  finger,  but  at  the  wall  or  the  ceiling  or  the  sky  or  any  suffi- 
ciently removed  expanse,  two  images  of  the  finger  will  be  seen, 
the  left  one  belonging  to  the  right  eye  and  the  right  one  to  the  left 
eye.     This  is  easily  proven  by  shutting  first  one  eye  and  then  the 

^  In  some  eyes  the  apparent  vertical  meridian  which  divides  the  retinas  into 
corresponding  halves  is  not  perfectly  vertical,  but  slightly  inclined  outward  at  the 
top.     This  would  effect  all  the  meridians  slightly,  but  the  effect  is  insignificant. 


PHYSIOLOGY.  25 

Other  and  observing  which  image  disappears/  To  confirm  this 
phenomenon  another  experiment  may  be  tried.  With  the  two 
forefingers  placed  directly  in  front  of  one,  in  the  median  plane  of 
the  head  one  at  arms  length,  the  other  one  half  that  distance 
(see  Fig.  14)  it  will  be  observed  that  if  the  farther  finger  is  seen 
single,  the  nearer  one  is  seen  double;  if  the  nearer  finger  is  ob- 


FiG.  14. — Experiment  to  illustrate  physiologic  diplopia.  If  the  far  finger  is 
looked  at  the  near  finger  is  seen  double  (crossed  diplopia);  if  the  near  finger  is 
looked  at,  the  far  finger  is  seen  double  (uncrossed  diplopia). 

served  this  one  will  be  seen  single,  but  the  farther  one  double; 
when  the  farther  one  is  seen  double,  the  right  image  disappears 
when  the  right  eye  is  closed;  that  is  to  say  the  images  are  un- 
crossed or  homonymous.  When  the  nearer  one  is  seen  double,  the 
right  image  disappears  when  the  left  eye  is  closed;  that  is  to  say 
the  images  are  crossed  or  heteronymous.  The  important  fact  to  be 
borne  in  mind  is  that  it  is  impossible  for  both  fingers  to  be  seen 
as  single  objects  at  the  same  time.  Therefore  it  is  evident  that 
when  we  look  directly  at  anything  we  see  it  single,  but  that  all 

'  Some  persons  find  difficulty  in  consciously  recognizing  the  two  images.  It  is  not 
uncommon  for  such  persons  to  habitually  neglect  one  image  until  it  finally  drops 
out  of  consciousness.     Hence  they  are  likely  to  become  either  right  or  left  eyed. 


26  ANATOMY  AND   PHYSIOLOGY. 

things  situated  at  that  same  instant  either  nearer  or  farther  away 
than  the  object  looked  at  are  seen  double  whether  consciously 
recognized  as  double  or  not.  Fortunately,  in  ordinary  every  day 
use  of  the  eyes  this  physiologic  diplopia  is  disregarded  because  of 
the  overwhelming  dominance  of  the  fusion  sense  and  single  vision 
results. 

ON  SYNERGISTIC  MUSCLES,  OR  THOSE  WHICH  ASSIST 
EACH  OTHER. 

It  has  been  shown  in  the  chapter  on  anatomy  and  physiology 
that  the  external  rectus  and  the  internal  rectus  have  purely 
lateral  action;  but  that  the  superior  rectus  moves  the  eyeball 
not  only  upward,  but  also  inward  (medianward)  while  the  inferior 
rectus  draws  the  eyeball  downward  and  also  inward  (median- 
ward).     Also,  that  the  superior  oblique  muscle  moves  the  cornea 

SIP  RCCTOS  /^vrOBl/QVl 

Up  ana /n  -      v  /       Vpa/idOut' 

Op  and  left.      \  /        UpondRifkL 


Ltr  I  yK n/Crn/ 


l/vr  RECTUS  SOP.OBLIQUE 

Down  and  /n  =  Down,  ond  Out-. 

Duwnitnd  Left.  J)  uun  and  Right. 

Fig.  15. — Showing  the  dominant  action  of  the  muscles  of^the  right  ej-e.  This 
diagram  is  based  on  the  presumption  that  the  eyes  are  in  the  priman'  position  when 
the  movement  in  the  various  directions  begins. 

downward  and  outward  (temporal ward)  and  the  inferior  oblique 
moves  the  eyeball  upward  and  outward  (temporalward) .  These 
movements  may  be  represented  diagramatically  as  in  Fig.  15. 
As  a  matter  of  convenience  and  memory  help  the  student  will  do 
well  to  remember  that  the  right  inferior  oblique  for  instance  moves 
the  right  eyeball  up  and  right  rather  than  up  and  out  or  temporal- 
ward.  The  same  is  true  of  all  other  motions  imparted  by  the 
muscles  to  the  globe. 


PHYSIOLOGY.  27 

Further  study  of  Fig.  15  (which  refers  to  the  right  eye) 
will  show  that  both  the  superior  rectus  and  the  inferior  oblique 
of  the  right  eye  are  elevators  of  that  eye  and  that  when  they  act 
together  they  rotate  the  eyeball  directly  upward,  their  torsional 
actions  in  opposite  directions  neutralizing  each  other.  These 
two  muscles  are  therefore  said  to  be  synergistic  muscles.  Similarly 
the  superior  oblique  and  the  inferior  rectus  of  the  right  eye  are 
both  depressors  of  the  right  globe  (their  torsional  effect  being 
neutralized)  and  they  also  are  synergistic  muscles.^ 


//vr.  oouQU£  svp.  fiecTus 

Up  and  Ouf  =  \  /      l^P  and/n  - 

Vp  UKd  left.      \  /       iiptr/xl/llffAl 


LEFT  ^2^:^^::^ xz /^yrnecrus  ^^^^^^ 


SUP.  OBUQt/£  /\f.  /iccms 

Down  and  Out.  Douin  o.?ui  /n- 

Domn  and  left.  Down  and  Higfit. 

Fig.  16. — Dominant  action  of  the  individual  muscles  of  the  left  eye. 

In  considering  Fig.  16  which  refers  to  the  left  eye,  it  will  be 
found  that  exactly  the  same  state  of  affairs  obtains  so  far  as 
the  left  eye  is  individually  concerned,  only  it  will  be  seen  at  a 
glance  that  while  the  right  superior  rectus  moves  the  right  globe 
up  and  left,  the  left  superior  rectus  moves  the  left  globe  up  and 
right.  The  same  difference  obtains  with  the  inferior  rectus  of 
the  two  eyes  and  with  both  obliques,  and  these  differences  must 
be  closely  observed  as  they  lead  directly  to  the  study  of  the  eyes 
as  a  pair. 

'  It  can  also  be  easily  seen  that  in  moving  the  right  eyeball  directly  to  the  right 
the  external  rectu  predominates  in  that  movement  but  the  superior  and  inferior 
obUque  by  joint  cont'iction  assist  in  that  movement;  also  that  in  the  movement 
of  the  right  eyeball  to  the  left,  the  internal  rectus  dominates  the  action  but  is 
assisted  by  the  joint  contraction  of  the  superior  and  inferior  rectus.  This  syner- 
gism obtains  in  every  eye  movement  that  is  made  and  there  is  no  movement  of  the 
eyeballs  in  which  but  one  muscle  is  the  sok  and  only  muscle  concerned. 


28  ANATOMY   AND    PHYSIOLOGY. 

ASSOCIATED  MUSCLES. 

If  Figs.  15  and  16  are  now  studied  side  by  side  it  will  be  seen 
at  once  that  in  the  movement  of  both  eyes  directly  to  the  right, 
the  muscles  that  predominate  in  this  action  are  the  right  external 
rectus  and  the  left  internal  rectus.  In  movements  to  the  direct 
left,  the  right  internal  rectus  and  the  left  external  rectus  dominate 
the  movement.  In  movement  of  the  eyes  up  and  to  the  right  the 
two  muscles  principally  concerned  are  the  right  inferior  oblique 

ijfana  l£fj-  LP  a>"i/^/(l/ir 

fi.suR  REC'ras      \  /    l. sop.  rectus 


BOTH                                                    \         /  Born 

EYTS  l£xrP,£CTi'S \^ /^TXT/fCCTOS  £y£s 

L£FT  H  l.\LTI£CTVS  /\  L  /VTfiECTOS  RIGHT 


i.sop.oei/iii/T     /  \    n.sop.oBLiQvE 

ff.  TVr.  PECTUS     /  \  / .  /,  J  E.  RECTUS 

DOWN  «"<i  L  EFT  D  0  [\N  <"''i  RIGHT 

Fig.  17. — Representing   Figs.  15  and  16  superimposed.     The  associated  muscles 
in  the  two  eyes  are  thus  graphically  shown. 

and  the  left  superior  rectus;  down  and  to  the  left,  the  right  inferior 
rectus  and  the  left  superior  oblique,  and  so  on  through  the  six 
principal  movements  of  the  eyes.  In  each  one  of  these  six 
principal  movements  of  the  eyes  two  muscles  are  primarily  active 
— one  in  each  eye.  This  yoking  of  one  muscle  in  one  eye  with 
another  in  the  fellow  eye  to  perfect  the  ease  of  binocular  move- 
ments is  known  as  association  of  the  muscles.  Hence  such  muscles 
are  designated  associated  muscles  (or  yoke  fellows).  Figs.  15  and  16 
may  now  be  superimposed  to  produce  (Fig.  17)  a  diagram  represent- 
ing perfectly  the  associated  muscles  in  both  eyes.     It  shows  that 


PHYSIOLOGY. 


29 


in  movements  of  the  eyeballs  up  and  to  the  right,  the  right  infe- 
rior oblique  and  the  left  superior  rectus  are  the  dominant  forces; 
in  movements  down  and  to  the  left,  the  right  inferior  rectus  and 


Fig.  18. — Bernheinier's  scheme  lo  illuslrale  the  action  of  the  associated  muscles 
in  lateral  movements  (lateral  conjugation)  and  in  convergence,  a,  Right  external 
rectus;  b,  right  internal  rectus;  c,  left  internal  rectus;  d,  left  e.xternal  rectus;  e,  third 
nerve  nucleus;  /,  communicating  fibres;  ,i^,  si.xth  nerve  nucleus;  h,  fimbriated  cells; 
/,  arborizing  ends  of  the  fibres  to  the  opposite  side  of  the  cerebral  cortex;  k,  cortical 
centers;  /,  aqueduct  of  Sylvius;  ni,  roof  of  he  corpora  rjuadrigemina.  (Graefe- 
Saemisch  Handbuch,  second  edition.) 

the  left  superior  oblique  do  most  of  the  work  and  so  on  through 
all  the  six  cardinal  movements  imparted  by  the  muscles  to  the 
eyes.     In  each  of  these  movements  as  shown  on  the  diagram, 


30  ANATOMY   AND    PHYSIOLOGY. 

the  muscles  shown  there  as  associated,  work  most  harmoniously 
together.  These  associated  movements  are  also  known  as  con- 
jugate movements. 

From  what  has  thus  far  been  said,  it  naturally  follows  that  the 
two  eyes  work  together  as  one,  as  Hering  has  said.  It  is  impos- 
sible for  one  eye  to  move  in  one  direction  without  the  other  one 
paralleling  its  action  in  every  particular.  A  nervous  impulse 
from  the  cortex  must  of  necessity  be  divided  equally  between  the 
two  eyes.  Hence  the  perfectness  of  the  conjugation  between  them. 
These  association  or  conjugate  movements  of  the  eyes  are  rep- 
resented in  all  likelihood  by  centers  in  the  anterior  central  as  well 
as  the  posterior  cortex.  Sherrington's,  and  Risien  Russell's  ex- 
periments both  strongly  support  this  idea^  (Fig.  i8). 
Five  conjugate    innervations  have  long  been  known,   namely: 

1.  Binocular  elevation. 

2.  Binocular  depression. 

3.  Binocular  right  rotation. 

4.  Binocular  left  rotation. 

5.  Convergence.     A  distinct  act. 

There  are  probably  a  number  of  others,  but  they  remain  at 
present  speculative. 

ANTAGONISTIC  MUSCLES. 

In  addition  to  synergistic  and  associated  action  of  the  muscles, 
it  is  well  to  keep  in  mind  always  the  antagonistic  action  as  set 
forth  in  the  following  table: 


Muscle. 

Antagonists. 

Internal  rectus. 

I. 

External  rectus. 

2. 

Superior  oblique 

2. 

Inferior  oblique. 

External  rectus. 

I. 

Internal  rectus. 

2. 

Superior  rectus. 

2. 

Inferior  rectus. 

*  There  may  be  sub-cortical  stations  for  additional  control  of  such  movements,  but 
of  such  connection  the  seeming  proof  is  much  less  probable. 


PHYSIOLOGY. 

I. 

2. 

I. 
2. 

Inferior  rectus. 
Superior  oblique 
Superior  rectus. 
Inferior  oblique. 

I. 
2. 
I. 
2. 

Inferior  oblique. 
Superior  rectus. 
Superior  oblique 
Inferior  rectus. 

31 


Superior  rectus. 
Inferior  rectus. 
Superior  oblique 
Inferior  oblique. 


The  figures  i  and  2  signify  primary  and  secondary  antagonists 
respectively. 

THE  STEREOSCOPE. 

The  most  important  information  on  the  distance  of  an  object 
is  furnished  us  by  the  degree  of  convergence  necessary  to  fix  it 


c 

) 

d' 

0' 

© 

/ 

a'                     d 

V 

I 

/\ 

4. 

I:   d" 

^      J 

c 

./■■     ^ 

Fig.  19. — Wheatstone's  stereoscope,  composed  of  two  plane  mirrors  d,  d'  and  d" 
which  are  at  right  angles  to  each  other.  The  eye  O'  sees  in  the  mirror  d'd"  the  picture 
hh'  and  projects  it  toff.  The  eye  O  sees  in  the  mirror  dd'  the  picture  aa'  and 
projects  it  toff  just  as  the  eye  O'  does;  the  two  images  are  fused  into  a  single  one, 
presenting  the  phenomenon  of  relief.  In  order  not  to  have  the  relief  reversed  (or 
pseudoscopic)  it  is  necessary  to  present  to  the  left  eye  the  image  intended  for  the 
right  eye  since  the  mirrors  reverse  the  images. 

binocularly.  When  we  fix  a  distant  object,  a  near  object  appears 
in  double  crossed  images.  Although  these  double  images  are  not 
often  perceived,  they  give  us,  nevertheless,  a  vague  idea  of  the 


32 


ANATOMY   AND    PHYSIOLOGY. 


distance  of  the  object,  for  they  furnish  a  pretty  accurate  impulse 
to  convergence,  and  thus  guided  we  converge  for  the  object  without 
much  effort.  So  that  two  visual  judgments  have  been  formed — 
one  for  the  remote  object  and  one  for  the  nearer  object,  and  the 
difference  between  the  two  judgments  furnishes  the  information  on 
which  we  base  our  estimate  of  the  distance  of  objects.  When  we 
look  at  an  object  having  considerable  depth  or  space,  or  at  a 
scene,  there  is  an  image  of  the  object  or  scene  formed  on  each 

retina.  These  two  images  are  not 
exactly  alike  because  they  are  taken 
from  different  points  of  view.  If  two 
cameras  are  placed  before  an  object 
or  a  scene  with  a  distance  between 
them  of  2  or  3  feet,  they  will  fairly 
well  present  two  great  eyes,  with  large 
interocular  distance.  The  pictures 
thus  taken  cannot  be  exactly  alike 
because  taken  from  different  points. 
They  will  differ  from  each  other 
exactly  as  the  two  retinal  images  of 
the  same  object  differ,  only  in  greater 
degree.  If  these  two  photographs  be 
binocularly  combined  in  a  stereo- 
scope they  ought  to  and  must  pro- 
duce a  visual  effect  exactly  like  an 
actual  object  or  scene,  for  in  looking  at  an  object  or  scene 
we  are  only  combining  retinal  images  exactly  like  these  pic- 
tures, because  they  are  taken  in  the  same  way.  The  advantage 
of  binocular  vision  was  made  clear  only  by  the  invention  of 
the  stereoscope  of  Wheatstone  in  1833  (Fig.  19).  With  this 
instrument  we  obtain  an  impression  of  depth  much  superior 
to  that  which  any  other  representation  can  give  of  it.  The 
stereoscope  facilitates  binocular  combinations  beyond  the  plane 
of  the  pictures.  The  refracting  stereoscopes  (Brewster's,  1849, 
Fig.  20)  by  means  of  lenses,  supplement  the  lenses  of 
the  eyes   and  thus  produce  on  the  retinas  perfect  images  of  a 


Fig.  20. — Brewster's  stereo- 
scope. The  pictures  c  and  d  are 
blended  or  fused  in  the  plane  gh. 


PHYSIOLOGY. 


33 


near  object,  although  the  eyes  are  looking  al  a  distant  object. 
The  lenses  also  enlarge  the  images  and  thus  complete  the  illusion 
of  a  natural  scene  or  object.  The  clinical  value  of  the  refracting 
stereoscope  is  indicated  by  the  number  of  modifications  that  it 
has  undergone.  The  Holmes  model  (Fig.  21)  is  the  one  ordi- 
narily found  in  the  shops.  Javal,  Parinaud,  George  Bull,  Richard 
Derby,  Oliver  and  many  others  have  all  brought  forward  various 
devices  to  adapt  the  stereoscope  to  every  day  ophthalmic  practice, 
each  with  its  own  peculiar  excellences.     The  one  disadvantage  of 


Fig.  21. — Holmes'  stereoscope. 


all  of  them  was  that  they  were  very  imperfectly,  if  at  all,  adaptable 
to  the  higher  degrees  of  deviation  of  the  ocular  axes  (hetero- 
phoria  and  heterotropia) .  Javal  was  the  only  one  who  met 
this  difficulty  with  his  hinged  stereoscope  w^ith  mirrors,  concerning 
which  he  writes: 

"In  spite  of  the  care  that  has  been  taken  to  increase  the  field 
of  the  stereoscope  by  the  employment  of  lenses  of  relatively  short 
foci,  it  often  happens  that  the  deviation  is  too  strong  to  enable 
one  to  use  a  stereoscope  which  has  lenses  at  all.  It  is  then  that 
one  finds  the  advantage  of  employing  my  stereoscope-a-charniere" 
3 


34  ANATOMY  AND   PHYSIOLOGY. 

About  ten  years  ago  Worth  carried  the  idea  further.  He 
put  two  of  Priestly  Smith's  fusion  tubes  on  a  hinge  and  bending 
each  tube  he  placed  a  mirror  at  the  bend,  making  an  adjustable 
reflecting  stereoscope.  It  has  one  advantage  over  Javal's  in 
that  the  brightness  of  the  images  may  be  varied  for  either  eye — 
a  point  of  value  in  the  orthoptic  treatment  of  strabismus. 

THE  EVOLUTION  OF  BINOCULAR  VISION. 

Binocular  single  vision  is  the  normal  state  of  human  eyes. 
This  is  because  of  the  partial  decussation  of  the  optic  nerve 
fibers  in  the  chiasm.  When  compared  with  the  visual  apparatus 
in  the  lower  animals  the  study  of  binocular  vision  takes  on  great 
interest.  The  gradual  evolution  of  the  invertebrate  eye  is  scienti- 
fically satisfactory.  The  transition  from  the  invertebrate  to  the 
vertebrate  eye  is  involved  in  some  doubt.  From  that  point  up- 
ward, however,  the  evolution  is  resumed  and  continues  very 
regularly.  In  the  lowest  class  of  vertebrates  (the  fishes)  the  eye 
is  probably  no  better  than  a  squid's.  Their  eyes  are  situated  on 
the  side  of  the  head  with  such  widely  divergent  axes  that  there 
is  no  overlapping  of  the  visual  fields  at  all.  There  is  no  consen- 
sual movement,  each  eye  being  absolutely  independent  of  the 
other.  There  is  no  common  field  of  view,  no  common  point  of 
sight,  no  corresponding  points  in  the  two  retinas;  hence  no  bin- 
ocular single  vision.  Leaving  out  amphibians  and  reptiles  (of 
which  we  know  little),  in  birds  binocular  vision  becomes  possible 
by  an  unique  arrangement  of  corresponding  points  about  a  very 
excentral  fovea,  though  their  optic  axes  are  widely  divergent. 
In  mammals  the  optic  axes  are  brought  around  more  and  more  to 
the  front  and  the  convergence  of  the  axes  on  a  point  of  sight  at 
infinity  becomes  easier  and  easier.  With  this  comes  the  gradual 
development  of  corresponding  points  about  a  more  highly 
organized  central  area  on  which  is  based  all  the  phenomena  of 
binocular  vision  and  the  visual  judgments  issuing  therefrom. 
Only  in  the  anthropoid  apes  do  we  find  the  eyes  ifairly  in  front 
with  optic  axes  parallel  in  the  position  of  rest.     There  is  too  at 


PHYSIOLOGY. 


35 


36  ANATOMY  AND    PHYSIOLOGY. 

this  Stage  a  much  more  highly  organized  spot  of  central  vision 
(fovea)  added,  which  is  one  of  the  essentials  in  what  ihe  psychol- 
ogist calls  the  faculty  of  attention.  The  existence  of  the  fovea 
is  necessary  to  the  concentration  of  attention  on  the  thing  looked 
at,  for  "how  could  we  attend  to  one  thing  if  all  other  things  were 
equally  distinctly  seen?"  The  work  of  Lindsay  Johnson^  has 
added  much  certainty  to  this  study.  Each  time  he  investigated 
the  fundus  oculi  of  the  more  than  200  animals  that  came  under 
his  observation,  he  measured  the  divergence  of  the  optic  axes 
by  means  of  a  special  contrivance  known  as  a  goniometer.  The 
results  of  this  tremendous  task  are  shown  in  Fig.  22.  On  the 
left  hand  of  the  chart  will  be  found  the  range  of  divergence  be- 
tween the  various  members  of  the  orders  taken  as  a  whole,  while 
on  the  right,  details  as  to  famihes  and  genera  axe  given.  It  will 
be  readily  seen  from  the  chart  that  the  higher  the  order  the 
nearer  the  axes  approach  parallel  vision,  although  the  range  in 
each  is  considerable,  and  each  one  to  some  extent  overlaps  the 
other.  It  will  also  be  noted  on  the  right  hand  that  the  degree  of 
divergence  for  the  hare  is  85  degrees,  for  the  giraffe  72  degrees, 
for  the  porcupine  45  degrees,  for  the  hedgehog  40  degrees,  for 
the  pig  ^;^  degrees,  for  the  wolf  25  degrees,  for  the  dog  20  degrees, 
for  the  fox  15  degrees,  for  the  cat  10  degrees,  and  for  the  diurnal 
monkeys  and  apes,  as  also  in  men,  zero,  or  parallelism  of  the 
optic  axes. 

In  the  development  of  the  human  embryo  there  can  be  followed 
the  same  evolution  in  one  species  that  is  above  outlined  in  all 
the  vertebrate.  The  eyes  develop  on  the  sides  of  the  head  as  in 
the  fish.  Gradually  with  the  formation  of  the  face  they  are 
brought  around  to  their  permanent  frontal  position  and  are  in 
place  about  the  end  of  the  second  month.  In  this  the  ontogeny 
agrees  with  the  philogeny  and  the  forward  rotation  of  the  optic 
axes  of  each  vertebrate  is  consistently  followed  in  the  developing 
human  enbryo. 

The  stimulus  to  the  animal  to  see  what  is  in  front  of  it  with 

'Taken  from  his  work,  "The  Comparative  Anatomy  of  the  MammaHan  Eye," 
London,  1901. 


PHYSIOLOGY.  37 

both  foveas  directed  exactly  to  the  one  point,  attains  its  highest 
development  in  the  anthropoid  apes  and  man. 

In  the  newborn  human  infant  there  is  no  coordination  of  the 
eyes.  After  the  first  week  of  life  the  babe  will  sometimes  fix 
a  small  electric  light  or  candle  momentarily,  but  only  momen- 
tarily. Then  the  eyes  will  wander  aimlessly  about,  being  sometimes 
in  convergence  and  sometimes  in  divergence.  By  the  end  of  the 
third  week  this  fixation  will  be  a  little  more  fixed  and  by  the  time 
the  sixth  to  the  eighth  week  is  reached  many  babes  will  fix  the 
small  electric  light  in  a  dark  room  and  maintain  the  fixation  for 
quite  a  time.  The  nurse  or  mother  will  state  at  this  time  that  the 
child  is  ''beginning  to  take  notice  of  things."  This  is  what  the 
psychologist  terms  "the  unfolding  of  the  faculty  of  attention." 
By  others  it  is  known  as  the  fusion  faculty.  This  faculty  is  not 
firmly  established  before  the  end  of  the  sixth  month  and  occasion- 
ally not  before  the  end  of  the  first  year,  and  even  then  slight  ill- 
nesses (especially  gastro-intestinal  ones)  may  temporarily  disturb  it 
gravely.  It  is  a  faculty  that  in  some  children  responds  rapidly 
to  training  as  late  as  the  sixth  or  seventh  year,  but  very  poorly 
after  that  period. 

Binocular  single  vision  therefore  may  be  defined  as  a  con- 
genitally  acquired  psychic  blending  of  the  two  sets  of  visual  impres- 
sions that  are  focussed  on  corresponding  positions  of  each  retina. 

TESTS  FOR  BINOCULAR  VISION. 

Of  all  the  tests  for  binocular  vision  or  perception  of  relief, 
Hering's  drop  test  is  probably  the  most  reliable,  for  in  most 
others  we  have  to  rely  upon 
the  patient's  statements  with- 
out being  able  to  verify  them. 
A  crude  model  (Fig.  23)  can 
easily  be  made  by  taking  a  fiat 
pasteboard  box  about  i  foot 

long,  2  inches  high  and  6  to  7     Fig.  23.— Hering's  binocular  vision  test  box. 

inches  wide,  made  concave  at  one  end  to  fit  tightly  against  the 
head.     From  the  other  end  two  wires  project  forward  and  out- 


38 


ANATOMY  AND    PHYSIOLOGY. 


ward  connected  at  their  ends  by  a    horizontal  thread  which  is 

provided  with  a  small  bead 
at  its  midpoint  for  the  pa- 
tient to  look  at  through  the 
box.  Small  objects,  such 
as  dried  peas  or  beans  or 
small  marbles  are  dropped 
by  the  examiner  from  one 
hand  to  the  other,  some 
beyond  the  thread  and 
others  between  it  and  the 
box.  taking  care  to  have 
those  which  fall  beyond  the 
thread  a  trifle  larger  than 
those  which  fall  inside  of 
it.     The  operator's    hands 

Fig.  24.-Bar  reading.  ^j^^^jj    ^^    entirely    OUt    of 

the  patient's  sight.  If  binocular  vision  exists,  the  patient  will 
almost  always  give  a  correct  answer  as  to  which  side  of  the 
thread  the  object  falls:  if 
not,  nearly  half  the  answers 
will  be  wrong. 

Javal's  bar  reading  is  a 
fair  test  for  single  binocular 
vision  (although  there  are 
those  who  claim  that  it  is 
really  more  a  test  of  rapid 
alternate  binocular  vision.) 
The  simplest  means  of 
using  the  test  is  a  flat  metal 
bent  spring,  1/2  inch  wide, 
to  be  held  by  the  thumb  on 
the  page  of  the  book  which 
is  being  read  (Fig.  24). 
The    idea    is    to   discover  i-ic-  25.— Remy's  Dipioscope. 

whether  the  patient  can  read  continuously  without  bobbing  his 


PHYSIOLOGY.  39 

head.  If  there  is  amblyopia  in  one  eye  the  patient  cannot  of 
course  read  that  part  of  the  print  which  lies  behind  the  arm  of 
the  spring  without  moving  his  head:  if  both  eyes  have  good 
visual  acuity  but  do  not  work  together,  there  must  either  be  a 
head  movement  or  a  hesitation  when  the  deviated  eye  has  to 
suddenly   take   up  fixation,   followed    immediately   by   another 


Fig.  26. — Bishop  Harman's  diaphragm  test. 

pause  when  the  first  eye  again  takes  up  fixation.  Remy's  diplo- 
scope  (Fig.  25)  and  Bishop  Harman's  diaphragm  test  (Fig.  26) 
are  both  evolutions  of  this  same  test.  Both  are  of  value  in  the 
examination  of  the  presence  of  binocular  single  vision  and  both 
will  be  referred  to  in  the  chapter  on  the  treatment  of  heterophoria 
or  strabismus. 


PART  II. 
STRUCTURAL  ANOMALIES;  PALSIES, 


OCULAR  PALSIES 


Ocular  palsies  arc  of  intracranial  or  of  orbital  origin.  The 
intracerebral  areas,  invaded  by  various  lesions,  include  the 
highest  cortical  centers,  the  centers  for  associated  movements, 
the  fibers  connecting  these  centers  with  the  oculo-muscular 
nuclei  in  the  4th  ventricle,  the  nuclei  themselves,  and  the 
trunks  of  the  nerves  to  the  ocular  muscles  anywhere  from  the 
4th  ventricle  to  their  point  of  escape  from  the  cranial  cavity 
into  the  orbit.  Lesions  of  the  nerve-trunks  consist  in  degen- 
eration of  the  nerve  itself,  or  in  interruption  of  their  function 
by  disease  in  their  neighborhood,  such  as  meningeal  exudate, 
thickening  of  the  periosteum,  neoplasms,  hemorrhages  and 
wounds;  also  by  vascular  changes,  such  as  atheroma,  aneurysm, 
emboli,  and  thrombi.  The  underlying  cause  is  generally  to  be 
found  in  constitutional  disease,  pre-eminently  syphilis  and  tuber- 
culosis. Strikingly  causative  in  this  class  are  tabes  and  general 
paralysis  of  the  insane,  the  rheumatic  diathesis,  basal  menin- 
gitis, and  brain  tumors.  Other  conditions  productive  of  ocular 
palsies  are  the  various  forms  of  intoxication,  diabetes,  nephritis, 
diphtheria,  influenza,  hysteria  and  many  of  the  rarer  diseases 
of  the  central  nervous  system.  The  most  recent  addition  to  the 
causes  of  ocular  palsies  is  the  injection  of  various  anesthetic 
solutions  into  the  intraspinal  canal  (so-called  spinal  anesthesia 
for  surgical  purposes).  These  palsies  appear  about  two  weeks 
after  the  intraspinal  injection  is  made  and  behave  very  much  like 
postdiphtheritic  palsies. 

Orbital  palsies  arise  from  some  local  cause  usually  situated  at 
the  entrance  of  the  nerve  into  the  orbit  through  the  superior 
orbital  fissure,  and  are  sometimes  due  to  an  affection  of  the 
nerve  itself,  at  other  times  the  result  of  pressure  upon  or  disease 
adjacent  to  the  nerve.     There  is  a  class  of  palsies  not  caused  by 

43 


44  STRUCTURAL  ANOMALIES;    PALSIES. 

influences  acting  in  the  orbit  but  on  the  nerve  within  the  muscle, 
which,  by  Mauthner  and  some  others,  are  termed  "peripheral," 
and  are  ascribed  to  rheumatism,  although  Mauthner  himself 
says  that  such  palsies  are  not  infrequently  the  forerunners  of 
some  serious  central  nervous  disease,  and  are  always  to  be  regarded 
with  suspicion.  It  is  our  own  belief  that  if  many  of  these  cases 
were  followed  out  for  a  number  of  years  until  their  real  origin 
became  apparent,  we  would  hear  less  of  "rheumatic"  palsies. 
Congenital  ocular  palsies  may  be : 

1.  Traumatic,  from  forceps  delivery. 

2.  Inflammatory,  affecting  the  nerve  directly  or  indirectly. 

3.  Neoplastic,  due  to  cranial  or  orbital  tumors. 

4.  Teratologic,  due  to  arrested  development. 

Ptosis. — An  exhaustive  study  of  paralysis  of  the  upper  lid 
would  be  out  of  place  in  a  monograph  on  affections  of  the  motility 
of  the  eye,  yet  a  brief  statement  of  the  principal  features  of  ptosis 
would  seem  to  be  appropriate.  On  page  7  it  was  stated  that 
the  superior  rectus  and  the  levator  palpebrse  are  connected  by 
bands  of  connective  tissue  just  anterior  to  the  meridian  of  the 
globe.  Therefore  paralytic  affection  of  one  will  be  manifest 
by  partial  or  complete  loss  of  function  of  the  other. 

Ptosis  is  congenital  or  acquired.  Congenital  ptosis  may  be :  of 
any  intensity,  but  is  generally  incomplete  and  double.  The  lightest 
cases  are  those  in  which,  through  hypertrophy,  abnormal  length 
or  loss  of  contractility,  the  elevation  of  the  lid  is  restricted. 
In  the  severer  grades  the  smooth  lid  hangs  over  the  ball,  is  without 
folds  and  can  be  elevated  only  by  the  aid  of  the  frontalis.  Con- 
genital ptosis  is  usually  associated  with  a  deficiency  in  upward 
movements  of  the  globe,  both  through  congenital  defect  in  the 
elevators  and  non-use.  Since  the  lid  covers  the  eyeball  no  need 
arises  for  turning  the  cornea  upward.  It  may  also  be  com- 
plicated by  other  muscular  paralysis,  (for  example,  all  of  the  3d 
nerve  muscles),  by  diminution  in  visual  acuity  and  by  nystagmus. 

In  Wilbrand  and  Saenger,  is  given  (ist  Abt.,  page  8^)  a  series 
of  instances  of  the  hereditary  form,  collected  from  the  literature. 
These  authors  state  that  it  is  almost  invariably  associated  with  other 


OCULAR   PALSIES. 


45 


defective  muscular  action,  but  does  not  involve  the  iris  or  the 
ciliary  muscle.  The  affection  is  passed  down  through  both  sexes, 
and  may  skip  a  generation.  It  is  more  common  among  the 
Jews  than  among  other  peoples.  They  found  the  causes  to  be 
underdevelopment  of  the  levator,  bifurcation,  union  with  other 
muscles,  abnormal  insertion,  and  absence  or  lack  of  development 
of  the  nerves,  or  the  nuclei  of  the  related  cortical  regions  (tem- 
poral fissure  and  angular  gyrus). 

Acquired  Ptosis. — During  birth,  instrumental  delivery  may  be 
responsible  for  producing  edema  or  hemorrhage  within  the  skull 


Fig.  27. — Ptosis  after  menin- 
gitis. Patient  of  Dr.  James  H. 
McKee. 


Fig.  28. — Bilateral  ptosis  with 
complete  ophthalmoplegia  externa 
chronica. 


by  which  the  nerves  in  their  origin  or  course  are  damaged;  or  by 
pressure  upon  the  muscle  within  the  orbit;  from  lesion  of  the 
levator  induced  by  wounds  to  the  muscle  or  its  tendon,  by  pres- 
sure, by  tumors,  by  intracranial  diseases  and  in  many  affections 
of  the  central  nervous  system,  notably  posterior  sclerosis  and 
multiple  sclerosis.  The  lesion  is  to  be  sought  in  the  cortex  of  the 
brain,  in  the  nuclei,  and  last  of  all  in  the  nerves  (Fig.  27).  It  also  ac- 
companies or  follows  infectious  diseases  and  other  states  such  as 
diphtheria,  toxemia,  and  influenza.  It  is  usually  double  except 
in  orbital  lesions,  gradual  in  onset,  of  prolonged  course,  and 
incurable  without  operation  (Fig.  28). 


46  STRUCTURAL  ANOMALIES;    PALSIES. 

Ptosis  is  the  most  jfrequent  variety  of  congenital  palsy.  Paral- 
ysis of  the  external  rectus  is  second  in  frequency.  Marina  men- 
tions as  quite  frequent,  conjugate  convergence  paralysis,  the  in 
tegrity  of  the  internal  recti  being  preserved.  Mauthner  and  Dufour 
consider  external  ophthalmoplegia  (paralysis  of  all  the  extrinsic 
muscles)  as  a  nuclear  disease;  Mobius  regards  it  as  a  special  in- 
fantile disappearance  of  the  nucleus,  and  recently  Simmerling  has 
found  true  disappearance  of  the  nucleus  with  degeneration  of 
some  of  its  fibers;  at  times  it  is  complicated  with  palsy  of  the  facial 
nerve.  Inability  to  turn  the  eye  upward  has  often  been  found  to 
co-exist  with  congenital  ptosis  and  autopsies  have  shown  absence 
of  the  superior  rectus  in  many  such  cases.  Perhaps  similar  de- 
fects lie  at  the  bottom  of  many  other  congenital  paralyses. 

SYMPTOMATOLOGY. 

The  main  symptoms  by  which  ocular  palsies  reveal  themselves 
are:  i.  Limitation  of  movement;  2.  false  fixation;  3.  diplopia; 
4.  vertigo;  5.  vicarious  rotation  of  the  head. 

Limitation  of  movement  in  the  direction  of  action  of  the 
affected  muscle  is  shown  when  a  test  object  held  in  the  median 
line  is  moved  toward  the  field  of  action  of  the  palsied  muscle. 
In  abducens  palsy  for  instance  the  sound  eye  follows  the  move- 
ment easily  as  far  as  the  limits  of  the  field  of  binocular  fixation, 
while  the  cornea  of  the  squinting  eye  will  be  seen  to  stop  at  the 
median  line;  or  if  it  can  be  rotated  further  in  that  direction,  it 
will  be  by  a  series  of  jerks  and  irregular  contractions. 

In  a  case  of  partial  paralysis,  the  limitation  of  movement  may 
be  so  slight  as  to  be  almost  invisible.  The  globe,  no  longer  under 
the  control  of  six  muscles,  is  rotated  from  the  primary  position 
to  a  secondary  one,  the  resultant  of  the  combined  action  of  the 
five  sound  muscles.  This  deviation  may  be  objectively  deter- 
mined roughly  by  inspection,  and  accurately  by  the  use  of  the 
perimeter  or  Stevens's  tropometer,  and  subjectively  by  the  de- 
gree of  prism  necessary  to  displace  the  image  of  the  affected 
eye  from  its  false  position  back  into  the  vertical  or  horizontal 
line,  or  to  fuse  it  with  the  true  image.     Except  in  frank  6th  nerve 


OCULAR    PALSIES.  47 

or  3d  nerve  palsies,  very  little  information  can  be  gained  by  the 
observation  of  the  limitation  of  movements,  because  all  the  eye 
movements  are  under  the  control  of  more  than  one  muscle. 
Therefore,  paralysis  of  one  muscle  may  be,  in  part,  compensated 
for  by  the  action  of  its  synergist.  Again,  the  arc  of  the  circle  of 
upward  and  downward  rotation  is  normally  much  less  than  the 
lateral,  and  imperfect  movement  is  less  easy  to  detect  in  vertical 
than  in  horizontal  palsies. 

Primary  and  Secondary  Deviation. — The  cornea  is  rotated 
by  the  sound  muscles  in  the  direction  opposite  to  the  affected 
muscle,  the  degree  of  rotation  and  forced  immobility  depending 
upon  the  completeness  of  the  paralysis  and  the  amount  of  sec- 
ondary contraction  of  the  antagonist  muscles.  This  is  known  as 
"primary"  deviation.  If  now  the  sound  eye  is  covered,  it  will 
be  seen  under  the  cover  to  have  assumed  the  squint  corresponding 
to  that  of  the  afifected  eye.  This  "secondary"  deviation  is  more 
pronounced  than  the  primary,  since  the  extremely  strong  innerva- 
tion necessary  to  stimulate  the  paralyzed  muscle  involves  over- 
action  of  these  muscles  in  the  sound  eye  acting  with  it  in  associated 
movements.  For  the  reasons  given  above,  the  rotation  of  the 
cornea  cannot  be  observed  with  accuracy  in  the  case  of  paralysis 
of  the  superior  and  inferior  recti  and  the  two  obliques,  and  oft- 
times  we  cannot  derive  much  advantage  from  this  measure. 

False  Fixation  or  Orientation. — Objects  in  space  cannot  be 
accurately  located  with  the  squinting  eye  because  their  images  do 
not  fall  upon  the  fovea,  but  upon  a  neighboring  portion  of  the 
retina,  in  a  direction  and  at  a  distance  from  the  fovea  depending 
upon  the  muscle  paralyzed  and  the  degree  of  the  paralysis.  The 
test  instituted  by  v.  Graefe,  and  called  by  him  the  "touch  test," 
consists  in  closing  the  sound  eye  and  at  once  requiring  the  patient 
to  point  toward  a  designated  object  in  the  field  governed  by  the 
muscle  involved.  Instead  of  indicating  the  true  position,  the 
finger  will  point  to  some  other  part  of  the  field  governed  by  the 
affected  muscle.  When  the  sound  eye  is  closed  and  the  patient 
attempts  to  walk  to  a  designated  object,  he  tends  to  a  course 
lying  in  the  field  of  the  paralyzed  muscle.     In  cases  of  long  stand- 


48  STRUCTURAL  ANOMALIES;    PALSIES. 

ing,  these  tests  are  worthless,  because  the  patient  has  learned  to 
use  his  judgment  and  to  make  allowance  for  false  projection. 

Diplopia.' — This  is  the  most  constant,  persistent  and  annoy- 
ing symptom  of  all  paralyses.  Two  images  (the  true  and  the 
false)  of  every  object  are  seen  in  that  part  of  the  field  into  which 
the  affected  eye  cannot  be  turned.  The  discrimination  by  the 
patient  of  the  true  from  the  false  image  is  not  always  possible, 
and  other  senses  than  that  of  sight  must  be  called  upon  to  aid  in 
the  discrimination.  The  physician  is  aided  in  his  diagnosis  by : 
I,  the  relative  position  of  the  two  images;  2,  their  relative  mova- 
bility  when  the  test-object  is  carried  in  all  directions;  3,  the  loss 
of  parallelism  of  the  vertical  or  horizontal  axes  of  the  two  images, 
this  loss  becoming  more  marked  in  the  periphery  of  the  binocular 
field;  4,  the  conscious  fixation,  or  the  patient's  testimony  as  to 
which  is  the  true  and  which  the  false  image.  In  some  cases  all 
tests  fail. 

Vertigo  depends  upon  false  projection  and  diplopia.  It  is 
most  annoying  in  the  early  stages  of  the  paralysis  and  with  few 
exceptions  becomes  less  and  less  troublesome  as  the  case  wears  on. 
It  disappears  promptly  and  entirely  upon  excluding  the  de- 
viating eye  from  the  act  of  vision,  and  partially  upon  excluding 
the  sound  eye.  The  mental  disturbances  are  at  times  so  great 
that  the  patient  is  discouraged  from  his  usual  pursuits,  and  shuns 
society,  seeking  seclusion  and  darkness. 

Vicarious  Rotation  of  the  Head. — In  order  to  supply  the 
function  of  the  silent  ocular  muscle,  the  head  is  rotated  by  the 
action  of  compensating  neck-muscles.  By  this  means  the  false 
image  may  be  made  to  fuse  with  the  true  one  over  a  much  larger 
portion  of  the  common  field  than  if  the  head  is  held  in  the  primary 
position,  and  considerable  diplopia  and  mental  confusion  are 
avoided.  The  secondary  head  position  depends  upon  the  muscle 
involved.  In  paralysis  of  an  elevator,  the  eye  is  turned  down 
and  the  head  therefore  thrown  backward  on  its  horizontal  axis; 
if  a  depressor,  the  reverse;  if  the  right  externus,  the  head  is  turned 
to  the  right  on  its  vertical  axis;  if  the  right  internus,  to  the  left; 

'  It  is  assumed  that  monocular  diplopia  is  not  present. 


OCULAR   PALSIES.  49 

if  the  left  externus,  lo  the  left;  if  the  left  internus,  to  the  right. 
While  these  compensatory  rotations  do  not  specifically  determine 
the  muscle  affected,  they  are  valuable  adjuncts  to  the  diagnosis, 
particularly  if  the  elevators  or  depressors  are  involved. 

DIAGNOSIS. 

In  the  diagnosis  of  ocular  palsies  the  art  of  diagnosis  by  ex- 
clusion is  carried  to  an  utmost  nicety.  With  this  purpose  in 
view  it  is  well  to  bear  always  in  mind  certain  factors,  namely:  i. 
The  law  of  projection.  2.  The  doctrine  of  corresponding 
retinal  points.  3.  The  synergistic  action  of  the  muscles.  4. 
The  antagonistic  action  of  the  muscles.  If  these  are  well  learned 
and  remembered  there  will  be  little  need  for  the  numerous 
mnemonics  or  memory  helps  offered  by  many  authors.  All  these 
four  factors  have  been  previously  gone  into,  but  the  student  will  do 
well  to  refresh  his  mind  about  them  before  attempting  to  diagnose 
any  ocular  palsy.  Another  series  of  facts  of  value  in  approaching 
this  subject  is  the  grouping  of  the  ocular  muscles  according  to  their 
predominant  action.  For  instance,  of  the  twelve  ocular  muscles 
it  will  readily  be  seen  that  four  of  them  are  lateral  rotators — 
namely,  the  two  external  and  the  two  internal  recti;  also  that  there 
are  four  whose  action  is  predominantly  to  elevate  the  globes — 
namely,  the  two  superior  recti  and  the  two  inferior  obliques;  and 
that  finally  there  are  four  which  principally  depress  the  globes^ 
namely,  the  two  inferior  recti  and  the  two  superior  obliques.  They 
may  be  arranged  as  follows: 

LATERAL   ROTATORS. 

Right  and  left  external  rectus. 
Right  and  left  internal  rectus. 

ELEVATORS. 

Right  and  left  superior  rectus. 
Right  and  left  inferior  oblique. 


50  STRUCTURAL  ANOMALIES;   PALSIES. 

DEPRESSORS. 

Right  and  left  inferior  rectus. 
Right  and  left  superior  oblique. 

The  convenience  of  this  arrangement  is  apparent  at  a  glance 
when  one  reflects  that  if  a  patient  complains  of  diplopia  on  look- 
ing to  the  right  or  left,  one  of  the  four  muscles  in  the  Lateral 
group  must  be  at  fault.  If  on  the  other  hand  the  complaint  is 
of  diplopia  on  looking  downward,  some  one  of  the  four  De- 
pressors is  under  suspicion;  while  if  the  complaint  is  of  diploia  on 
looking  upward  the  Elevator  group  will  furnish  the  affected 
muscle. 

These  groups  are  again  divided  into  pairs,  one  muscle  of  each 
pair  being  in  the  right  eye,  the  other  in  the  left  eye,  as  for  instance 
the  right  external  rectus  and  the  left  internal  rectus — or  the  right 
superior  rectus  and  the  left  inferior  oblique.  (See  the  chapter 
on  Associated  Muscles).^ 

So  that  with  the  muscles  divided  into  three  groups  and  six 
pairs,  one  should  be  able  by  a  simple  differentiation  (the  char- 
acter of  the  diplopia)  to  find  just  what  group,  then  what  pair, 
and  finally  what  muscle  is  involved  in  a  case'of  palsy. 

If,  for  instance,  a  patient  comes  complaining  of  double  vision 
on  looking  to  the  right,  the  group  of  lateral  rotators  must  be  at 
fault,  and  as  the  diplopia  is  greatest  in  the  right  field  either  one  of 
the  two  right  rotators  (dextraverters)  is  under  suspicion.  This 
narrows  the  diagnosis  down  to  the  right  external  or  the  left  internal 
rectus  and  the  final  decision  as  to  which  of  these  two  is  affected 
turns  on  whether  the  diplopia  is  crossed  (heteronymous)  or  un- 
crossed (homonymous).  In  the  former  case  it  is  the  internus, 
in  the  latter  the  externus  that  is  palsied. 

In  palsy  of  the  vertically  acting  muscles,  much  stress  has  been 
laid    in    former   years    on    whether   the   accompanying   vertical 

'  The  term  associated  antagonists  (borrowed  from  the  German)  is  an  unfortunate 
one  in  that  it  is  Ukely  to  create  in  the  mind  of  the  student  the  idea  that  the  muscles 
are  not  only  associated,  but  also  antagonistic.  The  latter  is  not  true.  They  are 
associated,  but  not  antagonistic — hence  our  belief  that  the  use  of  the  term  should  be 
discontinued. 


OCULAR    PALSIES.  5 1 

diplopia  was  also  crossed  or  uncrossed;  but  in  recent  years  it  has 
been  plainly  shown  that  extraneous  factors  may  be  at  work  that 
may  easily  confound  the  practitioner  if  he  relies  on  this  phenomenon 
too  much.  Study  of  the  vertical  character  of  the  diplopia,  alone, 
will  lead  to  a  certain  diagnosis.  Given,  therefore,  a  case  in  which 
the  patient  complains  of  double  vision  on  looking  down,  the  de- 
pressor group  must  be  interrogated.  We  know  that  either  one 
of  the  inferior  recti  or  superior  obliques  is  underacting.  The 
next  step  is  to  find  which  eye  beholds  the  lower  image,  for  if  a 
depressor  muscle  is  palsied  or  paretic,  the  eye  to  which  it  belongs 
cannot  be  rotated  downward  as  far  as  its  fellow,  and. therefore 
its  axis  pointing  higher  will  see  the  false  image  lower  than  the  true 
one.  For  illustration  let  us  assume  that  the  image  belonging  to 
the  right  eye  is  the  lower  one.  We  then  know  that  the  palsied  mus- 
cle is  in  this  eye  and  that  it  must  be  either  the  right  inferior  rectus 
or  the  right  superior  oblique.  The  final  decision  as  between 
these  two  turns  on  whether  the  area  of  greatest  vertical  diplopia 
is  down  and  to  the  right  or  down  and  to  the  left.  If  the  area  of 
greatest  vertical  diplopia  is  down  and  to  the  right,  it  means  that 
the  inferior  rectus  is  involved  and  that  the  antagonistic  muscles 
have  rotated  the  right  eyeball  up  and  to  the  left  and  that  there- 
fore by  the  law  of  projection  the  area  of  greatest  diplopia  must 
be  down  and  to  the  right.  If  the  area  of  greatest  vertical  diplo- 
pia in  this  same  given  case  were  down  and  to  the  left  (instead  of 
down  and  to  the  right)  it  would  imply  that  the  eyeball  had  been 
rotated  up  and  to  the  right  by  the  antagonistic  muscles  (as  in 
palsy  of  the  superior  oblique)  and  that  consequently  the  area  of 
greatest  vertical  diplopia  must  be  down  and  to  the  left. 

The  student  is  recommended  to  draw  a  diagram  as  in  Fig.  29 
and  indicate  the  amount  of  lateral  or  vertical  diplopia  present  in 
the  various  portions  of  the  binocular  visual  field.  If  a  note  is 
made  in  the  margin  as  to  which  is  right  and  left  and  whether 
the  images  are  crossed  or  uncrossed  and  in  the  case  of  vertical 
palsies  which  image  is  the  higher,  the  diagram  can  be  studied  after 
the  patient  has  left  the  surgeon's  consulting  room  and  a  certain 
diagnosis  arrived  at.     Thus  the  accompanying  diagram  would 


52 


STRUCTURAL   ANOMALIES;    PALSIES. 


indicate  palsy  of  the  right  externus  (Fig.  29).  If  the  images  were 
crossed  instead  of  uncrossed  as  noted  to  one  side,  the  diagram 
would  indicate  a  palsy  of  the  left  internus  (the  associated  muscle) 
(Fig.  30).  A  splendid  means  for  determining  not  only  the  rela- 
tion of  one  image  to  the  other  but  of  demonstrating  obliquity  of 
one  or  the  other  is  to  place  before  each  eye  a  compound  Maddox 


i     R 


I 

B 

w 

1             / 

1 

w 

1 

11 

1       \ 

n        I 

Fig.  2q. 


IMAGES 

Fig. 


CROSSED 


R 


rod,  one  of  red  color,  the  other  without  color.  In  this  way,  the 
amount  of  torsion  present  is  easily  read  off  from  the  trial  frame 
and  the  progress  of  the  case  toward  recovery  may  be  accurately 
followed  and  registered. 


SPECIAL  PARALYSES. 

Paralysis  of  the  Oculomotor  Nerve,  i.  Complete  Ptosis. — 
The  abnormally  smooth  upper  lid  lies  over  the  ball  unmoved  by 
the  levator.  It  can  be  partly  raised  by  forcible  contraction  of 
the  occipito-frontalis  and  the  superior  rectus.  That  the  partial 
elevation  is  due  in  great  part  to  the  former  muscle  can  be  readily 
demonstrated  by  pressure  upon  the  eyebrows,  which  will  pro- 
hibit action  of  the  frontalis.  The  patient  will  endeavor  to  com- 
pensate for  the  lost  action  of  the  levator  by  throwing  his  head 
backward.) 

2.  Deviation  and  Limitation  of  Mobility. — All  movement  of  the 
ball,  excepting  that  dependent  upon  the  superior  oblique  (4th 
nerve)  and  the  external  rectus  (6th  nerve)  is  abolished,  and  the 
cornea  is  rotated  outward  and  slightly  downward.     The  physi- 


OCULAR   PALSIES.  53 

ologic  action  of  the  superior  oblique  alone  is  well  shown  in  this 
paralysis.  The  effort  made  by  the  patient  to  turn  the  eye  farther 
out  and  down  results  in  slight  actual  movement  down  and  out, 
and  the  upper  end  of  the  vertical  meridian  of  the  cornea  will  be 
plainly  seen  to  turn  toward  the  median  line. 

3.  Dilatation  of  the  Pupil. — The  dilatation  is  moderate  and  is 
due  to  the  paralysis  of  the  circular  sphincter  pupillary  fibers.  Fur- 
ther dilatation  can  be  obtained  by  the  instillation  of  a  mydriatic, 
which  empties  the  blood-vessels  of  their  contents,  and  possibly 
stimulates  the  sympathetic  fibers  and  relaxes  the  choroid  generally. 
The  pupil  is  absolutely  unresponsive  to  light  admitted  directly  or 
consensually  through  communicating  fibers  from  the  3d  nerve 
of  the  opposite  side,  also  to  the  stimuli  of  convergence  and  accom- 
modation (the  response  to  the  associated  action  cannot,  of  course, 
be  elicited  in  paralysis  of  the  accommodation  and  internus). 

4.  Failure  of  Accommodation. — In  emmetropia  the  inaction  of  the 
ciliary  muscle  (cycloplegia)  consequent  upon  complete  3d  nerve 
palsy  does  not  diminish  the  previous  acuity  of  vision  for  distance; 
in  hypermetropia  the  amount  of  loss  depends  upon  the  degree  of 
defect;  in  myopia  of  less  than  i  diopter  it  has  no  appreciable  effect. 
In  estimating  the  near  point,  in  E.  and  H.  and  in  low  degrees  of 
M.  the  tests  should  ahvays  be  made  while  the  far  correction  is  worn, 
or  its  kind  and  degree  known  and  allowed  for.  The  estimation 
of  the  loss  is  readily  determined  by  restoring  the  reading  power 
with  a  glass  of  known  focal  length  and  then  measuring  the  dis- 
tance from  the  patient's  eye  that  the  print  can  be  read.  Thus  in 
E.  I -f  3  will  allow  reading  at  13";  in  H.  of  2,+  5  would  be  necessary; 
in  M.  of  3  D.  the  test  type  would  be  held  at  13"  (without  —3); 
in  M.  of  5,  —2  would  restore  the  reading  power  for  13". 

5.  Diplopia. — The  false  image  is  on  the  side  opposite  to  the 
affected  muscle,  i.e.,  crossed  and  on  a  level  with  the  true,  except- 
ing in  the  extreme  periphery,  when  it  may  be  slightly  higher  and 
tilted  away  from  the  true  one.  Wishart^  states  that  when  the 
image  of  the  affected  eye  is  straight  and  that  of  the  sound  eye 
tilted,  nuclear  lesion  of  the  same  side  as  the  palsied  eye  may  be 

'  Journ.  Nervous  and  Mental  Diseases,  Dec,  1897. 


54  STRUCTURAL  ANOMALIES;    PALSIES. 

diagnosed,  because  as  the  fibers  of  the  3d  nerve  diverge  to  the  nu- 
cleus, a  few  of  them  pass  through  the  raphe  and  cross  over  to  the 
nucleolus  for  the  inferior  oblique  in  the  opposite  nucleus,  and  the 
inferior  oblique  of  the  affected  eye  thus  escapes  involvement,  while 
the  inferior  oblique  of  the  sound  eye  is  palsied.  On  the  other 
hand,  tilting  of  the  image  of  the  affected  eye  indicates  a  lesion  of 
the  trunk  of  the  nerve,  and  the  inferior  oblique  of  the  affected  eye 
suffers  along  with  the  rest  of  the  3rd  nerve  muscles  of  that  eye. 
The  images  separate  from  each  other  the  farther  the  test-object 
is  .carried  toward  the  limit  of  the  fie'd  governed  by  the  paralyzed 
muscle.  In  paresis,  the  diplopia  begins  as  soon  as  the  middle  line 
is  crossed,  but  in  total  paralysis  the  field  of  diplopia  passes  beyond 
the  median  line,  and,  in  old  cases,  attended  with  secondary  con- 
traction, single  vision  is  unattainable.  The  slight  elevation  of 
the  false  image  is  caused  by  the  contraction  of  the  superior  oblique 
of  the  affected  eye.  In  the  middle  portions  of  the  field  the  verti- 
cal turning  of  this  muscle  is  concealed  by  the  stronger  action  of 
the  externus  in  turning  the  cornea  outward;  but  when  the  abduct- 
ing power  of  the  latter  is  exhausted,  the  vertical  action  of  the 
superior  oblique  becomes  manifest. 

RECURRENT  OCULO-MOTOR  PALSY. 

1.  Ophthalmoplegic  migraine.  Preceding  or  accompanying  the 
recurring  motor  paralyses  are  attacks  of  amblyopia,  scintillating 
scotoma,  hallucination  and  pain.  Its  characteristic  symptoms 
are,  as  implied  by  the  name:  i,  pain;  2,  paralysis.  The  pain  be- 
gins suddenly  in  the  region  of  the  head  supplied  by  the  first  two 
branches  of  the  5th  pair  of  nerves  of  one  side,  principally  the  first, 
is  intense,  of  variable  duration  and  usually  terminates  in  reflex 
vomiting.  The  paralysis,  usually  of  the  3d  nerve,  is  complete, 
involving  all  its  branches,  and  continuing  with  decreasing  severity 
for  several  weeks  or  months.  Recovery  is  usually  complete, 
especially  in  those  cases  in  which  the  intervals  between  the  attacks 
are  short  and  the  attacks  themselves  are  brief.  The  paralysis 
may  become  permanent  and  extend  to  other  ocular  muscles. 

2.  Recurrent   oculo-motor  palsy  appears   and   disappears   at 


OCULAR    PALSIES.  55 

irregular  intervals  from  childhood  to  adult  life,  the  paralysis  gen- 
erally increasing  in  severity  and  duration  with  each  attack,  until 
frequently,  when  the  patient  has  reached  manhood  or  woman- 
hood, the  palsy  is  complete  and  permanent.  It  is  always  unilat- 
eral and  always  affects  the  same  nerve.  It  may  be  an  early 
symptom  of  locomotor  ataxia  or  one  of  the  symptoms  of  central 
syphilis  and  brain  tumor  or  a  local  disturbance  in  the  vascular 
supply  of  the  3d  nerve  nucleus  in  the  anterior  part  of  the  floor 
of  the  4th  ventricle.  It  is  not  amenable  to  any  known  treatment 
Recurring  and  partial  ophthalmoplegia  interna  is  characterized 
by  partial  or  complete  paralysis  of  the  iris  and  ciliary  muscle. 
For  a  period  of  days  or  weeks  the  pupil  is  dilated  and  unre- 
sponsive to  light  and  the  stimulus  of  associated  action,  and  the 
accommodation  is  in  abeyance.  The  symptoms  entirely  disappear, 
to  recur  at  irregular  intervals.  The  disease  is  probably  nuclear 
in  origin,  and  may  be  an  early  symptom  of  central  nervous  disease, 
such  as  locomotor  ataxia  or  multiple  sclerosis.  Treatment  other 
than  local  applications  of  eserin  seems  to  have  no  influence.  ^ 

PARALYSIS  OF  INDWIDUAL  BRANCHES  OF  THE  MOTOR 

OCULI. 

Internal  Rectus. — Inward  movement  of  the  cornea  past  the 
middle  line  is  limited  or  abolished.  The  face  is  turned  toward 
the  opposite  side,  the  diplopia  is  crossed  and  is  found  in  the  field 
governed  by  the  paralyzed  intefnus,  in  which  direction  the  false 
image  separates  more  and  more  from  the  true  one.  The  two  images 
are  on  a  horizontal  line  over  the  major  part  of  the  diplopic  field. 
At  the  extreme  periphery  the  false  is  slightly  higher  than  the  true 
image,  and  its  vertical  meridian  is  tilted  away  from  it.  For  ex- 
ample, paralysis  of  internus  of  the  right  eye :  the  cornea  is  turned 
outward  and  cannot  be  rotated  inward  past  the  median  line; 
rotation  in  all  other  directions  unrestricted;  the  false  image  is  to 
the  left  of  the  true,  on  a  level  with  it,  and  separates  from  it  the 
farther  the  test-object  (candle-light)  is  carried  to  the  left,  where  it 

'This  disease  was  first  described  by  Hansell  in  the  Ophthalmic  Record  for 
April,  1898. 


56  STRUCTURAL  ANOMALIES;    PALSIES. 

becomes  slightly  tilted,  its  upper  extremity  outward.  In  order  to 
compensate  for  the  abnormal  divergence  of  the  eye,  the  face  is 
turned  to  the  left  on  its  vertical  axis;  diplopia  commences  in  the 
middle  line;  or,  in  old  cases,  where  secondary  contraction  of  the 
externus  has  set  in,  diplopia  is  seen  over  the  entire  field.  Paral- 
ysis of  the  internal  rectus,  unassociated  with  palsy  of  some  or  all 
of  the  others  supplied  by  the  3d  nerve  of  this  same  side,  or  with 
the  opposite  internus  (paralysis  of  convergence)  is  extremely  rare. 
The  lesion  may  be  a  change  in  the  muscular  structure  itself,  con- 
genital, idiopathic,  traumatic,  or  due  to  an  exceedingly  fine  nuclear 
disease. 

Superior  Rectus. — When  the  gaze  is  directed  upward,  the 
sound  eye  follows  the  test-object,  but  the  cornea  of  the  affected  eye 
stops  at  the  horizontal  line  and  the  efforts  to  continue  its  upward 
turning  result  in  divergence.  Diplopia  is  found  in  the  upper 
half  of  the  field  of  vision.  The  false  image  moves  farther  from 
the  true  as  the  light  is  carried  upward,  the  former  indicating  the 
affected  eye  by  its  more  rapid  movement  and  greater  elevation. 
Its  upper  end  is  tilted  toward  the  temporal  side.  It  is  above 
and  crossed.  The  vertical  distance  is  greater  in  abduction,  the 
obliquity  in  adduction,  and  the  horizontal  separation  diminishes 
to  each  side.  The  head  is  tilted  backward  on  its  horizontal 
axis,  and  slightly  toward  the  paralyzed  side.  In  diagnosing 
paralytic  from  functional  disease  of  the  superior  rectus,  the  extent 
of  the  field  of  diplopia  is  an  important  feature.  In  paralysis,  the 
false  image  leaves  the  true  below  or  at  the  horizontal  line.  Again, 
in  paralysis,  efforts  to  turn  the  eye  upward  result  in  a  rotation 
upward  and  outward.  The  field  of  greatest  diplopia  or  vertical 
separation  is  up  and  to  the  right  for  the  right  eye,  and  up  and  to 
the  left  for  the  left  eye.  In  functional  disease,  the  limitation 
of  rotation  is  not  manifest,  and  can  be  determined  only  by  care- 
ful measurement  with  the  perimeter  or  tropometer.  The  onset 
of  paralysis  is  sudden;  it  is  preceded  or  accompanied  by  headache 
of  a  few  hours  or  days  and  may  be  associated  with  symptoms  of 
some  general  disease.  A  history  of  traumatism  or  disease  of  the 
nervous  system  may  be  elicited.     In  functional  disease  complaint 


OCULAR   PALSIES. 


57 


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Plate  i.— Position  of  the  images  in  palsy  of  the  indixidual  muscles  of  the  nght 
eye.  A,  Right  external  rectus;  B,  right  internal  rectus;  C,  right  superior  rectus; 
D,  right  inferior  rectus;  £,  right  superior  oblique;  F,  right  inferior  oblique. 


58  STRUCTURAL  ANOMALIES;  PALSIES. 

is  seldom  made  of  diplopia,  and  the  patient  will  probably  give 
the  history  of  long-continued  headache,  asthenopia,  and  reflex 
nervous  symptoms. 

Inferior  Rectus. — The  movement  of  the  eye  downward  is  limited, 
especially  in  abduction.  The  eye  is  lightly  diverged,  and  the 
diplopia  is  in  the  lower  half  of  the  field,  the  lower  image  belonging 
to  the  affected  eye,  with  its  upper  end  tilted  toward  the  temple. 
As  the  eye  is  adducted,  the  distance  between  the  images  decreases. 
The  head  is  tilted  upward  and  toward  the  affected  side.  In 
abduction,  the  false  image  becomes  more  tilted,  the  tilting  dimin- 
ishing when  the  object  is  moved  to  the  side  opposite  the  affected 
eye.  The  field  of  greatest  diplopia  is  down  and  to  the  right  for 
the  right  eye,  and  down  and  to  the  left  for  the  left  eye. 

Inferior  Oblique. — The  elevation  of  the  eye  is  limited,  es- 
pecially in  adduction,  although  no  deviation  of  the  eye  is  apparent. 
Diplopia  is  in  the  upper  half  of  the  field,  the  false  image,  tilted 
temporalward,  is  above  the  true  and  on  the  side  of  the  diseased 
eye.  The  vertical  difference  between  the  images  increases  and 
the  inclination  of  the  false  image  decreases  upon  looking  upward 
and  toward  the  sound  side.  The  field  of  greatest  diplopia  is  up 
and  to  the  left  for  the  right  eye,  and  up  and  to  the  right  for  the 
left  eye  (Plates  i  and  2).  .' 

For  the  prognosis  and  treatment  of  paralysis  of  the  oculo-motor 
nerve,  and  of  the  individual  muscles  under  its  control,  see  the 
last  two  paragraphs  in  this  chapter. 

TROCHLEARIS  PALSY. 

A  patient  presenting  paralysis  of  the  right  superior  oblique 
muscle  will  complain  of  diplopia  on  looking  down.  It  will  be 
found  that  the  lower  image  which  belongs  to  the  affected  (right, 
for  example)  eye,  is  inclined  to  the  left,  and  that  the  vertical 
distance  between  the  images  increases  as  the  eye  is  depressed  and 
adducted.  Abduction  will  increase  the  obliquity  of  the  image. 
The  head  is  tilted  toward  the  healthy  eye  and  the  face  is  turned 
down  and  toward  the  aft'ected  side.  The  limitation  of  movement 
of  the  eye  will  become  apparent  when  extreme  down  and  inward 


OCULAR   PALSIES. 


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Plate  2. — Position  of  the  images  in  palsy  of  the  individual  muscles  of  the  left 
eye.  _  A,  Left  external  rectus;  5,  left  internal  rectus;  C,  left  superior  rectus;  D,  left 
inferior  rectus;  £,  left  superior  obhque;  b\  left  inferior  oblique. 


6o  STRUCTURAL  ANOMALIES;   PALSIES. 

rotation  is  attempted,  and  on  looking  down  the  patient  will  see 
things  lower  than  they  ought  to  be.  The  field  of  greatest  diplopia 
will  be  down  and  to  the  left  for  the  right  eye,  and  down  and  to  the 
right  for  the  left  eye.  If  palsy  of  the  superior  oblique  muscle 
occurs  as  an  isolated  paralysis,  the  patient  can,  by  inclining  the 
head  downward  and  to  the  right  or  left,  produce  fusion  of  the 
images;  and  if  the  palsy  be  a  transient  one,  it  may  thus  never  come 
to  the  notice  of  the  surgeon.  However,  isolated  trochlearis  palsy 
as  a  focal  symptom  is  rather  uncommon.  The  trochlearis  is 
frequently  palsied,  in  conjunction  with  muscles  of  the  3d  nerve 
group. 

The  features  of  individual  paralysis  of  the  superior  oblique  are 
well  shown  in  the  following  history  taken  from  our  records. 

March  6,  1896.  J.  M.,  aged  forty-three.  For  three  months  he 
has  had  diplopia —  one  image  above  the  other.  V.  R.  20/50,  partly, 
L.  20/200;  low  myopia  and  astigmatism;  full  vision  with  correction; 
no  disease  of  the  media  or  eyegrounds.  Covering  the  right  eye 
with  the  blue  and  the  left  with  the  red  glass  and  testing  with  the 
candle  flame,  the  red  light  separated  from  the  blue  in  the  lower 
field,  the  upper  end  tilted  toward  the  blue,  always  homonymous 
in  the  left  field,  the  distance  between  them  increasing  the  farther 
the  candle  was  carried  down  toward  the  right.  When  the  image 
had  reached  20  degrees  to  the  right,  the  false  image  became 
crossed  over,  and  when  carried  to  the  left  it  crossed  at  30  degrees. 
The  movement  of  the  eye  down  and  in  was  limited.  The  di- 
plopia when  first  noticed  was  vertical.  A  prism  of  6  degrees  base 
down,  combined  with  i  degree  base  in,  in  front  of  the  left  eye, 
fused  the  images  in  the  median  field.  The  diagnosis  in  this  case 
rested  between  paralysis  of  the  inferior  rectus  and  paralysis  of  the 
superior  oblique.  That  is,  since  downward  movement  of  the 
left  eye  was  limited,  evidently  one  or  both  of  the  depressors  must 
have  been  affected.  The  normal  action  of  the  superior  oblique 
is  to  turn  the  cornea  down  and  out,  with  the  upper  end  of  its  verti- 
cal meridian  tilted  inward;  of  the  inferior  rectus,  to  turn  the 
cornea  down  and  in,  with  the  upper  end  of  its  vertical  meridian 
out.     In  paralysis,  therefore,  of  the  superior  oblique,  the  eye 


OCULAR    PALSIES.  Gl 

would  be  turned  in  rather  than  out,  and  the  images  would  be 
homonymous,  as  in  the  above  case.  In  paralysis  of  the  inferior 
rectus,  movement  down  and  in  would  be  limited  and  the  images 
would  be  crossed.  In  both  cases  the  false  image  would  be  tilted 
toward  the  true.  With  the  field  of  greatest  diplopia  down  and  to 
the  right  and  the  left  image  the  lower,  the  left  superior  oblique 
was  plainly  shown  to  be  the  affected  muscle.  The  lesion,  in  this 
case,  may  be  basal  or  nuclear.  It  is  impossible  to  tell  exactly  its 
character,  since  the  paralysis  remained  an  isolated  one,  without 
complications.  The  patient  had  a  syphilitic  history,  but  did  not 
improve  under  large  doses  of  iodid  of  potassium  and  bichlorid  of 
mercury,  nor  did  the  addition  of  strychnin  improve  the  symptoms. 

ABDUCENS  PALSY. 

1.  The  constant  sign  is  homonymous  lateral  diplopia,  for  objects 
at  all  distances.  The  distance  between  the  images  widens  as  the 
object  is  carried  away  and  to  the  side  of  the  affected  muscle  in  the 
horizontal  plane.  In  the  oblique  positions,  for  example,  up  and 
out,  when  the  upper  ends  of  the  vertical  merdian  incline  toward 
each  other  or  diverge  from  each  other.  This  tilting  is  slight  and 
unimportant  for  the  diagnosis,  since  it  may  also  be  due  to  com- 
plicating paralyses  or  unequal  insertions  of  the  muscles.  The 
false  image  is  on  the  side  of  the  affected  muscle  (homonymous). 
It  moves,  while  the  true  image  remains  fixed,  the  increasing  sepa- 
ration of  the  two  images  being  always  due  to  the  movement 
of  the  false. 

2.  Limitation  of  Movement. — In  complete  palsy  the  cornea  can- 
not be  rotated  outward  past  the  median  line. 

3.  The  cornea  of  the  affected  eye  is  inclined  toward  the  median 
line — convergent  squint. 

4.  False  Projection. — Images  are  not  formed  on  the  fovea,  but 
on  the  nasal  side  of  the  fovea — hence  the  image  is  projected  into 
the  temporal  field  and  the  brain  is  misled  as  to  its  position. 

5.  Secondary  deviation  inward,  of  higher  degree  than  the  pri- 
mary. 

6.  Vicarious  Rotation. — The  face  is  inclined  toward  the  right. 


62  STRUCTURAL   ANOMALIES;    PALSIES. 

in  palsy  of  the  right  cxterniis;  to  the  left,  in  palsy  of  the  left 
externus. 

The  long  course  of  the  6th  nerve  at  the  base  of  the  brain  renders 
it  peculiarly  liable  to  arrest  of  function  during  disease,  or  from 
traumatism  to  the  skull.  Indeed,  the  external  rectus  leads  in  the 
order  of  frequency  of  individual  dcular  palsies,  the  order  being 
external  rectus  first,  then  unilateral  oculo-motor  pasy,  paralysis 
of  the  superior  oblique,  the  inferior  rectus,  the  superior  rectus, 
the  internal  rectus,  and  the  inferior  oblique.  Duane  (Knapp's 
Arch,  of  Ophlhal.,  1894,  p.  61)  would  award  to  the  superior  rectus 
second  instead  of  third  place.  Convergent  strabismus  will  be 
simulated  as  the  eyes  are  moved  toward  the  palsied  side. 

Abducens  palsy  is  commonly  seen  after  fracture,  or  accompany- 
ing a  syphilitic  or  other  inflammatory  process  at  the  base.  It  also 
occurs  with  diseases  of  the  pons.  Peripheral  or  orbital  abducens 
palsy,  when  not  rheumatic  in  character,  is  said  by  Wood  to 
indicate  syphilis  in  adults  and  tubercular  disease  in  children. 
However,  in  the  latter  connection,  it  must  not  be  forgotten  that 
abducens  palsy  in  children  is  not  infrequently  congenital,  and 
may  also  be  traceable  to  forceps  delivery  (Marina). 

If  paralysis  of  the  external  rectus  is  not  peripheral,  basal,  or 
pontine,  the  lesion  resides  in  the  nucleus,  the  cortex,  or  the  con- 
necting tracts,  in  any  of  which  cases,  if  the  origin  be  not  specific 
or  traumatic,  the  prognosis  is  highly  unfavorable  and  ominous  of 
evil  for  the  near  future. 

The  treatment  of  this  particular  palsy  differs  in  no  wise  from 
that  of  the  other  ocular  paralyses,  outlined  in  the  chapter  on 
Treatment. 

The  following  instance  of  isolated  paralysis  of  the  external 
rectus  is  taken  from  our  records: 

Case  I. — January  30,  1896.  J.  S.,  aged  sixty-five,  widower, 
engineer  of  a  shifting  or  yard  engine.  Has  always  been  an 
unusually  healthy  man,  no  subjective  or  objective  testimony  of 
rheumatism,  syphilis,  or  tabes.  Four  days  ago  while  at  work  on 
his  engine,  objects  began  to  appear  double,  and  the  confusion 
became  so  great  within  an  hour  that  he  was  compelled  to  quit 


OCULAR    PALSIES.  63 

work.  The  anterior  ocular  segment  of  both  eyes  was  normal; 
pupils  4  mm.,  and  regularly  round;  V  equals  O.D.  and  O.S. 
5/36.  With  1. 00  D.S.  equals  5/6,  ocular  movements  were 
smoothly  and  completely  executed  in  all  meridians  save  in  move- 
ment to  the  left,  when  the  left  rectus  externus  refused  to  carry 
that  eye  more  than  5  mm.  beyond  the  median  line. 

The  ophthatmoscope  showed  clear  media  and  normal  fundi. 
With  a  red  glass  before  the  right  eye,  there  was  shown  homony- 
mous double  vision,  the  distance  between  the  images  increasing 
as  the  candle  was  carried  to  the  left.  There  was  no  upward  or 
downward  displacement  of  the  false  image,  nor  was  it  tilted. 
A  30  degree  prism,  base  out,  before  the  left  eye  fused  the  images 
at  4  meters;  but  the  patient,  even  by  the  fourth  day,  had  learned 
that  by  turning  his  face  toward  the  left  he  could  fuse  images  and 
avoid  diplopia.  Patient  was  ordered  1/16  grain  of  biniodid  of 
mercury,  and  strychnin  in  increasing  doses  three  times  a  day. 
Urinalysis,  made  by  his  general  medical  adviser,  shows  neither 
sugar  nor  albumin,  but  reveals  an  excess  of  uric  acid. 

Four  days  later,  fuses  images  with  11  degree  prism;  twenty- 
eight  days  later,  fuses  images  with  5  degree  prism. 

The  patient  did  not  return  for  further  observation.  The  fact 
that  the  patient  had  been  a  railroad  man  all  his  life,  that  the  palsy 
was  in  all  likelihood  non-focal,  and  that  it  disappeared  so  rapidly 
under  biniodid  of  mercury,  would  indicate  that  the  foregoing 
was  an  instance  of  specific  abducens  palsy. 

Case  2. — Abducens  paralysis  due  to  traumatism  of  the  skull. 
M.  J.,  aged  twenty-five,  applied  at  the  Polyclinic  Hospital,  De- 
cember 15,  1897,  complaining  of  constant  diplopia.  He  stated 
.that  on  December  8,  while  skating,  he  fell  and  struck  the  left  side 
of  his  head  on  the  ice.  He  was  dazed  for  a  short  time,  but  recovered 
and  noticed  nothing  unusual  until  evening,  when  objects  became 
double  and  remained  so.  The  right  eye  was  converged ;  the  cornea 
could  not  be  moved  past  the  median  line;  there  was  homonymous 
diplopia  on  the  right  side  of  the  field.  Media  and  eye-grounds 
normal.  The  lesion  was  probably  basal  and  consisted  of  minute 
hemorrhage  either  in  the  sheath  or  pressing  upon  the  trunk  of 


64  STRUCTURAL  ANOMALIES;   PALSIES. 

the  6th  nerve  on  the  right  side.  No  cerebral  symptoms  devel- 
oped and  there  were  no  other  complications.  This,  then,  is  an 
instance  of  traumatic  paralysis  occurring  in  the  long  course  of 
the  6th  nerve,  at  the  base  of  the  brain,  from  hemorrhage  due  to 
traumatism  of  the  left  side  of  the  skull.  The  final  outcome  of 
the  case  is  unknown. 

Inasmuch  as  the  nucleus  of  the  6th  nerve  is  said  to  be  the  center 
for  conjugate  deviation,  a  few  words  may  here  be  said  of 

CONJUGATE  PALSIES. 

Inability  to  move  the  eyes  in  association  to  the  right,  or,  as  the 
case  may  be,  to  the  left  beyond  the  median  line,  is  sometimes  seen 
in  individuals  who  nevertheless  converge  close  up  to  the  ordinary 
convergence  near  point.  This  paralysis  of  synchronous  action 
of  one  internal  rectus  and  the  external  rectus  of  the  other  eye  is 
known  as  conjugate  palsy,  and  may  follow  upon  lesions  in  the 
cortex,  the  corona  radiata,  the  internal  capsule,  or  the  pons.  It 
is  not  an  uncommon  symptom  in  gross  lesions  of  the  cerebrum 
and  the  pons,  although  the  conjugate  palsies  secondary  to  cere- 
bral lesions  are  exactly  the  reverse  of  those  seen  in  diseases  of 
the  pons.  Swanzy  (Diseases  of  the  Eye,  fourth  edition)  contrasts 
the  association  of  the  palsies  with  their  casual  lesions  as  follows: 

Cerebral  /  Destructive. — Eye  turned  away  from  palsied  side. 
Lesions.  \  Irritative. — Eyes  turned  toward  convulsed  side. 
Pontine    f  Destructive. — -Eyes  turned  toward  palsied  side. 
Lesions.    1   Irritative. — Eyes  turned  from  convulsed  side. 

Wernicke  (Nervous  Diseases,  by  Dercum)  speaks  of  conjugate 
palsy  of  upward  and  downward  movements  of  the  eyes  as  being 
secondary  to  disease  of  the  corpus  striatum  and  of  the  optic 
thalamus. 

PARALYSIS  OF  CONVERGENCE. 

A  woman,  aged  twenty-four,  was  under  the  care  of  Dr.  Dercum, 
at  the  Jefferson  Hospital,  on  account  of  inability  to  walk.  Ex- 
amination revealed  that   the  eyes  and  their  appendages  were 


OCULAR   PALSIES.  65 

normal  in  every  respect,  with  the  exception  that  the  patient  had 
lost  absolutely  all  power  of  convergence.  She  could  follow  with 
both  eyes  a  test-object  moved  to  the  right,  left,  above,  or  below, 
the  optic  axes  remaining  parallel  throughout  all  these  movements; 
but  when  the  test-object  was  moved  in  the  median  line  from  the 
distant  to  the  near  point,  she  altogether  failed  to  follow  the  move- 
ments with  either  eye.  She  had  no  diplopia  in  any  direction, 
and  no  ocular  paralysis.  The  optic  axes  remained  parallel  in  all 
movements,  hence  the  image  of  the  test-object  fell  on  correspond- 
ing parts  of  each  retina.  The  symptom  probably  arose  from 
cerebellar  disease. 

CONJUGATE  VERTICAL  PARALYSIS. 

March,  1895,  J.  B.,  aged  thirty-five,  complained  of  diplopia. 
Vision,  right  20/30;  left  hypertropia  6  degrees,  exotropia  4  degrees, 
from  paralysis  of  the  right  superior  oblique.  There  was,  in 
addition,  complete  paralysis  of  upward  movement  of  both  eyes.  An 
object  held  above  the  horizontal  line  could  not  be  followed  by 
either  cornea,  and  efforts  to  look  up  resulted  only  in  partial  con- 
traction of  the  levator  palpebrae.  In  April,  1897,  divergence  and 
upward  deviation  of  the  left  eye  marked;  vision  of  the  right  had 
fallen  to  20/40,  but  remained  full  in  the  left;  ophthalmoscope 
showed  commencing  atrophy  of  the  right  optic  nerve ;  in  the  left 
retina,  the  arteries  were  smaller  than  normal,  but  not  markedly 
so;  both  fields  concentrically  contracted  for  white  and  colors,  right 
decidedly;  pupils  responsive  to  light  and  accommodation,  but 
sluggish.  In  October,  1897,  vision  in  both  eyes  had  fallen  to 
20/50;  left  eye  diverged  and  rotated  slightly  downward;  upward 
movement  abohshed  as  before,  downward  movement  limited; 
optic  nerve  atrophy  had  further  advanced.  There  was  also  in- 
coordination of  extremities,  and  walking  was  on  this  account 
difficult.  The  knee  jerks  were  exaggerated.  This  is  a  case  of 
advancing  ophthalmoplegia  and  optic  nerve  atrophy,  the  symp- 
toms of  which  were  preceded,  for  some  years,  by  loss  of  upward 
movement  in  both  eyes.  The  patient  had  no  history  of  specific 
infection  or  constitutional  disease. 
5 


66  STRUCTURAL  ANOMALIES;   PALSIES. 

TROGNOSIS. 

Prognosis  in  ocular  palsies  hinges  on  whether  the  paralysis  be: 
I.  Acute  or  chronic;  2.  individual  or  associated;  3.  trau- 
matic or  idiopathic;^  4.  due  to  a  central  or  peripheral  lesion. 

It  is  further  influenced  by  the  nature  of  the  general  disease- 
process  of  which  it  may  be  a  symptom. 

An  acute  individual  palsy,  if  traumatic  or  peripheral,  offers  in 
many  cases  a  reasonably  hopeful  outlook.  Especially  is  this  the 
case  if  the  patient  is  the  subject  of  a  traumatism,  or  of  syphilis, 
rheumatism,  or  tabes.  In  the  latter  case,  the  palsy  is  likely  of 
a  peripheral  nature,  and  though  the  prognosis  as  to  the  paralysis 
itself  is  favorable,  it  is  important  to  remember  that  a  transient 
external  ocular  palsy  may  be  an  early  and  significant  symptom  of 
locomotor  ataxia,  and  should  never  be  disregarded.  Acute  pal- 
sies of  higher  origin  (basal,  nuclear,  or  fascicular)  are  to  be  re- 
garded with  apprehension;  and  though  they  often  prove  tran- 
sitory, they  more  frequently  portend  intracranial  mischief— syph- 
ilitic, hemorrhagic,  inflammatory,  or  neoplastic  in  character — 
and  thus  become  symptoms  of  great  value  in  estimating  the  prob- 
able nature  of  obscure  central  lesions. 

An  acute  associated  paralysis,  or  conjugate  palsy,  while  of  itself 
of  no  special  importance,  and  though  not  infrequently  transient, 
is  like  the  foregoing,  ominous  for  the  future,  and  should  invari- 
ably lead  to  thorough-going  investigation  of  the  functions  of  the 
patient's  nervous  system.     It  is  occasionally  hysteric  in  origin. 

Chronic  paralyses,  of  whatever  character,  are  gloomy  affairs, 
promising  little  for  the  present  and  less  for  the  future.  If  the 
palsy  be  an  individual  or  isolated  one,  it  is  apt  to  be  accompanied 
by  secondary  contraction  of  the  antagonistic  muscle  of  the  same 
eye.  Some  people  live  through  a  long  and  busy  career  with  palsy 
of  one  or  more  of  the  extrinsic  eye-muscles,  and  suffer  little  or  no 
discomfort  therefrom  after  the  acute  stage  is  passed,  but  this  is 
exceptional.  Oftener  some  grave  nervous  malady  unfolds  its 
features,  and  the  case  drags  its  weary  length  along,  or  in  the  midst 

*  Idiopathic,  here  used  in  the  sense  of  a  paralysis  occurring  without  demonstrable 
lesion  in  a  previously  healthy  person. 


OCULAR   PALSIES.  67 

of  life  the  patient  may  be  in  death.      Such  sudden  termination  is 
the  rule  in  paralyses  occurring  in  arterio-sclerotic  individuals. 

TREATMENT. 

As  to  treatment,  ocular  palsies  arrange  themselves  in  two  classes : 
those  in  which  the  origin  is  more  or  less  apparent,  offering  oppor- 
tunity for  rational  treatment,  and  those  in  which  the  obscurity 
surrounding  the  case  compels  empirical  therapy. 

Fortunately  for  both  surgeon  and  patient,  this  phase  of  the  sub- 
ject is  much  simplified  by  the  aid  of  statistics,  which  show  the 
predominant  influence  of  syphilis  in  the  production  of  paralyses 
of  the  ocular  muscles.  According  to  Alexander  (Syphilis  und 
Auge),  59.4  per  cent,  of  all  ocular  palsies  are  specific,  the  oculo- 
motor being  most  frequently  selected  by  the  disease.  Vigorous 
anti-syphilitic  medication  is,  therefore,  indicated  in  all  ocular 
palsies  that  are  not  traumatic,  or  cannot  be  shown  to  be  distinctly 
rheumatic,  tubercular,  or  gouty;  and  the  caprice  of  the  surgeon 
will  largely  dictate  what  shall  be  the  mercurial  or  iodin  prepara- 
tion used,  likewise  the  mode  of  its  application.  Moreover,  mer- 
cury or  iodin  will  be  preferred  as  the  palsy  is  a  secondary  or  terti- 
ary syphilitic  phenomenon;  and  it  is  well  to  bear  in  mind  that  all 
medication  aimed  at  ocular  palsies  (and  specific  treatment  in 
particular)  is  more  likely  to  be  fruitful  of  results  if  assisted  with 
Turkish  baths  and  hot  packs,  and  other  such  measures  as  will 
promote  increased  functional  activity  of  the  skin.  By  this  means 
most  heroic  internal  treatment  will  often  be  generously  tolerated. 
Recently  salvarsan  has  been  extolled  as  of  high  value  in  syphilitic 
palsies  but  as  2  or  3  cases  of  ocular  palsy  are  alleged  to  have 
followed  upon  its  use  it  will  be  wise  to  wait  for  complete  and 
satisfactory  demonstration  of  its  unfailing  usefulness.  It  is  well 
to  bear  in  mind  that  the  very  first  thing  to  be  done  in  the  treat- 
ment of  any  ocular  palsy  is  to  have  the  patient  wear  a  blinder 
over  the  eye  to  which  belongs  the  palsied  muscle  or  muscles. 
This  will  immediately  relieve  the  nausea  and  headache  due  to 
the  diplopia  and  false  projection. 

Isolated  palsies  occurring  in  adult  life  in  an  apparently  healthy 


68  STRUCTURAL   ANOMALIES;    PALSIES. 

middle-aged  individual  should  invariably  arouse  suspicion  of, 
and  thorough  search  for,  tabes,  or  general  paresis  which,  if  the 
suspicion  be  confirmed,  calls  for  anti-syphilitic  treatment  in  fully 
90  per  cent,  of  all  cases  (according  to  Erb  and  Fournier).  Every 
such  suspect  deserves  careful  interrogation  of  the  pupil  reflex  to 
light  and  accommodation,  and  of  the  patellar  tendon  reflexes. 

Essential  rheumatic  palsies  (a  class  that  is  yearly  growing  pro- 
portionately smaller)  yield  generally  to  salicylates  or  iodids,  the 
former  in  the  acute,  the  latter  in  the  chronic  forms  of  the  disorder. 
Other  rheumatic  remedies  have  been  favorably  mentioned  from 
time  to  time. 

When  paralysis  of  an  ocular  muscle  is  the  result  of  encroach- 
ment of  a  tubercular  focus  upon  the  nucleus  or  trunk  of  the  nerve 
supplying  the  palsied  muscles,  treatment  is  of  little  avail;  happily, 
such  conditions  are  rare. 

Palsies  of  gouty  origin  are  commonly  the  peripheral  mani- 
festations of  an  obliterating  endarteritis  or  hemorrhage  in  that 
part  of  the  floor  of  the  4th  ventricle  in  which  the  3d,  4th  and  6th 
nerve  nuclei  are  located.  If  the  arterio-sclerosis  be  not  too  ad- 
vanced, much  benefit  and  even  complete  recovery  may  follow 
upon  the  active  use  of  absorbents  and  diaphoretics,  at  the  same 
time  guarding  well  the  heart  with  digitalis  or  strychnin.  This 
treatment  is  also  applicable  to  the  palsies  associated  with  the  em- 
boli and  thrombi  common  to  cardio-vascular  disease. 

The  treatment  of  palsies  secondary  to  fracture  of  the  cranium, 
either  in  the  fronto-motor  region  of  the  calvarium  or  at  the  basis 
cranii,  is  embraced  in  the  general  treatment  of  the  fracture  itself — 
namely,  rest  in  bed,  antiphlogistics  and  absorbents,  or  surgical 
interference.  The  same  management  holds  good  for  the  palsies 
seen  with  orbital  or  sphenoidal  fractures.  If  the  nerve  trunk  or 
trunks  be  lacerated,  treatment  will  accomplish  little,  while 
antiphlogistics  and  absorbents  will  go  far  toward  restoring  func- 
tion if  its  arrest  be  due  to  the  pressure  of  hemorrhage  or  inflam- 
matory exudate.  For  those  palsies  that  accompany  inflamma- 
tions or  tumors  of  the  brain  and  its  membranes,  the  treatment 
must  be  aimed  at  the  major  affection.     If  the  process  be  a  specific 


OCULAR   PALSIES.  69 

one,  its  therapy  is  simple.  If  it  prove  tubercular,  rheumatic, 
gouty,  arterio-sclerotic,  senile,  or  neoplastic,  symptomatic  treat- 
ment only  is  called  for,  and  will  often  prove  unavailing.  Palsies 
resulting  from  the  introduction  of  the  various  local  anesthetics 
into  the  spinal  canal  (spinal  anesthesia  for  surgical  purposes) 
have  a  spontaneous  tendency  to  recover.  The  externi  are  most 
frequently  involved.  Three  to  six  weeks  usually  ensue  before 
binocular  single  vision  is  restored. 

There  remains  to  be  mentioned  in  the  therapy  of  these  condi- 
tions, strychnin  and  electricity. 

The  value  of  strychnin  in  restoring  palsied  ocular  muscles  has, 
perhaps,  been  over-estimated.  This  may  be  due,  in  part,  to  the 
fact  that  it  has  been  exhibited  indiscriminately  in  all  forms  of 
palsy,  whether  cortical,  fascicular,  nuclear,  or  peripheral.  It  is 
in  the  latter  class  only  that  it  is  of  marked  value,  although  its  use 
is  admissible  in  the  acute  stages  of  almost  any  palsy.  A  method 
that  is  highly  esteemed  is  to  order  i  gr.  of  strychnia  in  i  ounce  of 
water,  beginning  whh  a  lo-drop  dose  (gr.  1/48),  three  times  daily, 
and  increasing  the  dose  i  drop  each  day  until  toxic  symptoms 
appear. 

As  to  electricity,  faradism  is  most  popular.  A  strength  of 
I  mp.  should  never  be  exceeded.  If,  as  some  prefer,  the  slowly 
interrupted  constant  current  be  used,  3  mps.  is  all  that  will 
usually  be  borne  wuth  comfort;  the  cathode  to  be  used  over  the 
closed  lid  and  the  anode  (or  indifferent  pole)  over  the  correspond- 
ing temple  or  mastoid.  The  quantity  of  current  that  really 
passes  through  the  affected  muscle  is  uncertain.  Some  surgeons 
prefer  to  place  the  anode  on  the  sclera  directly  over  the  palsied 
muscle  after  cocainizing  the  conjunctiva. 

It  is  ofttimes  necessary,  in  addition  to  the  medical  treatment  of 
the  paralysis  itself,  to  relieve  the  annoyance  which  the  diplopia  and 
vertigo  bring  with  them.  If  the  palsy  be  slight,  amounting  only 
to  a  paresis,  prisms  which  fuse  the  images — and  are  properly 
placed  in  an  ordinary  spectacle  frame — may  be  worn,  and  the 
patient  thus  rendered  comfortable  until  such  time  as  the  cure 
may  be  accomplished.     When  the  diplopia  cannot  be  thus  over- 


70  STRUCTURAL   ANOMALIES;    PALSIES. 

come,  it  is,  as  we  have  already  said,  best  to  exclude  the  paralytic 
eye  from  all  efforts  at  binocular  vision  by  placing  before  it,  in 
a  spectacle  frame,  a  piece  of  ground  glass. 

In  practising  the  mechanical  treatment  suggested  by  Michel, 
the  eye  is  cocainized  and  the  conjunctiva  seized  near  the  insertion 
of  the  palsied  muscle,  when  the  eyeball  is  drawn  forcibly  as  far 
as  possible  beyond  the  limit  of  contraction  and  then  back  again. 
Michel  recommends  daily  use  of  the  movements  for  about  a 
minute  each  time. 

In  a  general  way  it  may  be  said  that  most  ocular  palsies  are 
from  two  to  twelve  weeks  in  recovering,  so  that  the  surgeon  will 
do  well  to  be  guarded  in  discussing  this  phase  of  the  question 
with  the  patient. 

In  long-standing  paralyses,  operation  offers  the  best  results. 
Section  of  the  antagonist,  combined  with  advancement  of  the 
affected  muscle  and  adjoining  capsule  and  conjunctiva,  affords 
the  latter  the  most  favorable  mechanical  conditions  for  work. 
This  presupposes,  however,  some  slight  degree  of  contractility, 
consequently  complete  paralyses  are  incurable  by  operation. 

SPASM  OF  THE  OCULAR  MUSCLES. 

Primary  spasm  of  individual  ocular  muscles  has  been  described 
from  time  to  time  by  various  writers.  This  must  be  distinguished 
from  the  over-action  of  a  muscle  that  results  from  over-develop- 
ment in  the  muscle  itself  or  from  its  insertion  too  near  the  cornea 
so  that  its  mechanical  purchase  is  abnormally  increased.  Pri- 
mary spasm  is  rare  indeed.  It  has  been  recorded  as  occurring 
in  chorea,  meningitis  and  other  irritative  brain  lesions.  The 
spastic  oculomuscular  conditions  occurring  in  hysteria  never 
affect  single  muscles. 

Secondary  spasm  giving  rise  to  the  phenomenon  in  ocular 
palsies  known  as  secondary  deviation  is  common  enough  and 
at  times  quite  marked. 

NYSTAGMUS. 
Nystagmus  is  a  disturbance  of  associated  movements  tremor- 
like in  character.     It  may  be  lateral,  vertical,  rotational  (rotary 


OCULAR   PALSIES.  7 1 

or  wheel-like  or  torsional)  or  irregular.  The  binocular  variety 
is  usually  met  with  although  about  sixty  cases  of  the  unilateral 
variety  have  been  recorded.  The  rapidity  of  the  excursions 
varies  from  5  to  300  or  more  per  minute.  They  are  best  studied 
through  the  ordinary  ophthalmometer,  but  any  of  the  numerous 
corneal  microscopes  answer  quite  as  well.  The  principal 
symptom  is  poor  vision,  with  sometimes  vertigo  and  compensa- 
tory movements  of  the  head.  The  main  causes  are  defects  in  the 
transparency  of  the  media — congenital  defects  (spasmus  nutans), 
occupational  (miner's  nystagmus)  ataxic  conditions — labarynthian 
disease  and  certain  central  nervous  diseases,  such  as  Friederich's 
ataxia  and  preeminently  multiple  or  disseminate  sclerosis.  The 
treatment  will  be  determined  by  the  etiologic  factors — operation 
when  feasible  when  the  defects  in  the  media  are  remediable, 
changes  of  occupation,  treatment  of  labarynthian  disease,  etc. 


>r 


PART  III. 
FUNCTIONAL  ANOMALIES 


HETEROPHORIA. 
HETEROTROPIA. 


HETEROPHORIA, 


GENERAL  CONSIDERATIONS. 

In  the  study  of  the  relation  of  the  muscles  to  each  other  in 
states  of  abnormal  tension  and  relaxation  (but  without  paralysis) , 
we  leave  the  clearly  defined  field  of  recognized  symptoms  and 
conditions,  and  enter  that  of  uncertainty,  vagueness,  and  specula- 
tion; we  pass  from  the  logical  results  of  anatomic  changes  to  the 
confused  manifestations  of  unknown  psychologic  disturbances. 
We  do  not  deal  with  demonstrable  lesions  of  the  muscular  or 
nervous  system,  but  with  tendencies  to  inco()rdination,  the  result  of 
innervational  peculiarities  that  thus  far  have  been  untraceable 
by  the  dissector's  knife  or  physiologist's  microscope.  We  are 
brought  face  to  face  with  the  ocular  complications  of  disordered 
health,  of  inherited  or  acquired  abnormal  susceptibility,  of 
illogical  and  uncommon  results  of  common  causes,  of  individual 
idiosyncrasies — in  a  word,  of  unbalanced  nerve-action.  While  it 
is  not  disputed  that  functional  muscular  anomalies  follow  known 
causes  accprding  to  known  principles  of  cause  and  effect,  it  is 
maintained  that  some  of  the  most  difficult  problems  offered 
for  solution  cannot  be  explained  by  any  satisfactory  theory. 
Obstacles  surround  the  examination  and  treatment  of  every 
case  and  can  only  be  overcome  by  repeated  trials  with  modern 
diagnostic  methods  and  the  persistent  applications  of  physiologic 
and  conservative  remedies.  The  individual  element  must  not 
be  lost  sight  of,  and  every  factor,  ocular  and  extraocular,  that 
can  have  a  bearing  on  the  solution  thoroughly  investigated. 
The  oculist  is  not  the  refractor  or  the  tenotomist  alone,  but  is 
the  physician  as  well. 

Functional  deviations  are  so  intimately  bound  up  with  the  re- 
fractive status  as  to  compel  frequent  mention  of  the  latter  in 
discussing  the  various  forms  of  muscular  imbalance.     Indeed, 

75 


76  .  FUNCTIONAL   ANOMALIES. 

no  problem  in  hcterophoria  is  free  from  the  complicating  influence 
of  the  action  of  the  ciliary  muscle,  whether  the  eye  be  emmetropic 
or  not.  The  importance  of  this  relation  is  so  great  that  some 
authorities  maintain  today  that  all  muscular  "imbalance"  pro- 
ceeds from  errors  of  refraction,  and  that  the  persistent  wear  of 
correcting  lenses  will  ultimately  dissipate  the  hcterophoria. 
Functional  deviations  of  the  eye  depend,  further,  for  their  solution 
upon  heredity,  age,  sex,  social  condition,  temperament,  physique, 
vocation,  hours  of  work,  mental  worry,  and  numerous  other 
minor  factors.  It  will  thus  be  readily  seen  that  they  are  not  so 
simple  in  their  causes  and  treatment  as  has  been  suggested  by 
some  authors.  Many  of  the  older  writers  looked  upon  such 
deviations  of  the  ocular  muscles  as  symptoms  of  a  lowering  of  the 
general  nervous  tone  (whims  of  the  nervous  system,  as  some 
have  called  them),  or  of  some  general  pathologic  process;  and 
although  later  methods  and  up-to-date  instruments  of  precision 
have  plainly  shown  that  a  goodly  number  of  heterophorias  are 
not  symptomatic,  but  are  substantive  conditions  attended  by  a 
train  of  their  own  symptoms,  the  view  of  these  older  writers  was 
not  without  foundation,  and  it  deserves  particular  emphasis 
in  this  day  of  exceeding  specialism. 

Muscular  Balance. — The  eyes  may  be  said  to  be  swung  and 
held  taut  in  the  orbit  by  a  delicate  muscular  harness  and  the 
orbital  fascia.  The  four  recti  muscles  in  combination  tend  to 
draw  the  globe  backward  into  the  orbit,  which  action  is  opposed 
in  greater  or  less  degree  by  the  tendency  of  the  superior  and  infe- 
rior oblique  to  bring  the  globe  forward.  Hence,  a  slight  degree 
of  contraction  of  all  the  muscles  is  necessary  to  maintain  the  globe 
in  the  proper  position  during  all  waking  hours.  This  process, 
simultaneously  active  in  both  orbits,  produces  coordination  of  the 
visual  axes,  so  that  when  the  eyes  are  directed  toward  an  object, 
their  axes  will  meet  exactly  in  that  object,  and  the  eyes  are  said 
to  be  balanced,  or  in  equilibrium. 

It  is  important  to  remember  in  this  connection  that  the  direction 
of  the  visual  axes  when  the  eyes  are  in  the  anatomical  position 
of  rest  (resulting  from  the  form  of  the  orbit,  the  insertion  of  the 


HETEROPHORLA.. 


/  / 


optic  nerve  and  the  natural  length  of  the  muscles  when  not  inner- 
vated), is  generally  divergent,  rarely  parallel,  and  hardly  ever 
convergent.  But  the  function  of  normal  eyes  never  allows  in- 
dependent deviation,  hence  the  parallel  direction  demanded  for 
distance  can  never  be  abandoned  while  we  are  awake,  and  the 
unconscious  innervational  habit  pulls  the  eyes  from  the  anatom- 
ical position  of  rest  to  parallelism,  which  is  the  functional  posi- 
tion of  rest;  functional,  because  the  function  of  the  eyes  has 
produced  it,  and  position  of  rest,  because  the  position  assumed 
by  habit  and  unconscious  innervation  is  free  from  all  exertion. 

Any  disturbance  of  the  factors  just  mentioned  will  cause  muscu- 
lar imbalance,  and  yet  want  of  muscular  balance  is  not  incom- 
patible with  perfect  binocular  vision,  for,  in  many  cases,  visual 
axes  that  tend  to  deviate  are  brought  back  to  parallelism  by 
increased  innervation  to  a  given  muscle  or  group  of  muscles,  and 
it  is  this  necessary  extra  outlay  of  nervous  energy  that  frequently 
brings  on  asthenopia  in  small  degrees  of  muscular  imbalance. 

Functional  disorders  of  coordination  are  manifest  or  latent. 
There  may  be  an  actual  turning  of  one  optic  axis  from  the  other, 
involving  a  loss  of  associated  movement,  or  the  want  of  coordina- 
tion may  show  itself  as  nothing  more  than  a  tendency  to  deviation. 
Between  these  two  extremes  of  want  of  equilibrium  (the  one  re- 
presenting the  accomplished  strabismus,  the  other  latent  overac- 
tion  or  underaction  of  synergist  muscles)  is  a  middle  stage, 
characterized  by  the  development  of  either  the  deviation  tendency 
or  the  squint,  according  to  the  demand  made  on  the  different 
muscles;  for  example,  the  insufficiency  of  the  internal  recti  for 
near  work,  described  by  v.  Graefe  forty  years  ago.  The  study 
of  this  subject  will  be  simplified  if  the  student  will  bear  in  mind 
that  functional  want  of  equilibrium  concerns  in  all  cases  the 
destruction  of  the  normal  relation  between  two  sets  of  opposing 
muscles  rather  than  the  insufficient  or  overaction  of  any  one  muscle. 
Thus,  in  esophoria  we  are  dealing  with  the  power  of  convergence, 
and  not  the  strength  of  the  internal  recti.  It  is  unscientific  to 
attempt  to  separate  the  muscular  from  the  innervational  apparatus, 
the   more  so  as  the  latter  comprises  both  the  fusion-force  and 


78  FUNCTIONAL  ANOMALIES. 

the  impulse  conveyed  by  the  nerve-trunks;  and  equally  futile 
is  it  to  speak  of  one  muscle  as  having  more  power,  as  measured  by 
prisms,  than  its  corresponding  muscle  in  the  other  eye. 

The  various  gradations  from  the  slightest  tendency  of  the  optic 
axes  to  turn  from  equilibriurn  to  the  highest  degree  of  permanent 
squint,  are  but  steps  in  the  same  direction,  or  degrees  of  the  one 
affection,  and,  in  great  part,  the  causes  which  underlie  the  one 
grade  are  found  to  produce  all  the  others.     For  instance,  a  tend- 
ency to  turn  the  visual  axes  toward  each  other  has,  as  its  funda- 
mental  cause,   hyperopia.     The   degree   of   inward   turning   or 
tendency  is  determined  largely  by  the  personal  equation.     Many 
hyperopes   have   absolutely   no   want   of   equilibrium,   and   yet 
others,  even  with  low  grades  of  hyperopia,  develop  marked  mus- 
cular disorders.     It  has  been  contended  that  because  hyperopia 
does  not  produce  a  squint  in  every  instance,  the  squint  must  have 
some  other  cause,  but  it  is  well  known  that  the  same  cause 
produces  different  effects  according  to  individual  characteristics. 
A  low  grade  of  hyperopia  in  a  nervous  or  overwrought  disposition 
will  give  rise  to  serious  reflex  neuroses,  whereas  the  same  degree 
of  hyperopia  in  a  constitution  robust,  strong,  and  resisting,  will 
have  no  symptoms  whatever.     Again,  a  high  grade  of  hyperopia 
is,  in  some,  perfectly  consistent  with  equilibrium  of  the  muscles, 
while,  in  others,  it  is  the  cause  of  decided  strabismus.     This 
individuality  can  only  be  described  in  vague  terms.     It  is  known 
as  a  neurotic  disposition,  an  enfeebled,  unresisting  nature  and 
susceptibility  to  disease  or  an  exaggeration  of  reflex  excitability. 
Therefore,  when  all  circumstances  are  favorable,  reflex  neurosis 
may  arise  from  muscular  anomaly,  and  there  is  no  doubt  that,  in 
a  few  instances,  the  claims  made  by  enthusiastically  credulous 
writers  are  justified,  but  such  cases  are  exceptional  in  even  the 
largest  experience,  and  the  theory  that  a  considerable  proportion 
of  the  insane,  of  the  epileptic,  of  the  choreic,  owe  their  disease 
wholly  to  the  existence  of  either  a  refractive  error  or  a  consequent 
muscular  anomaly,  is  dangerous  and  unsound. 

In  examining  patients  who  have  no  organic  disease  of  the  eye 
or  its  environment,  but  suffer  from  reflex  headaches  and  annoyances 


HETEROPHORIA.  79 

of  various  kinds,  estimation  of  the  condition  of  refraction  and  of 
the  ocular  muscles  should  be  among  the  earliest  findings.  The 
investigation  of  the  muscular  status  should  be  made  both  before 
and  after  the  mydriatics  are  instilled,  because  of  the  direct  in- 
fluence these  drugs  have  in  many  cases  upon  both  the  kind  and 
degree  of  the  defect. 

The  nomenclature  of  anomalies  of  the  ocular  muscles  has  re- 
ceived a  decided  impulse  in  the  past  25  years.  For  functional 
deviations  Stevens  has  suggested  a  classification  that  has  met  with 
quite  general  acceptance  in  America  and  England.  It  is  as 
follows: 

Orthophoria,  perfect  binocular  balance. 

Heterophoria,  imperfect  binocular  balance.  Heterophoria 
presents  many  varieties,  namely: 

Hyperphoria,  a  tendency  of  the  visual  axis  of  one  eye  to  deviate 
above  that  of  the  other. 

Hypophoria,  a  tendency  of  the  visual  axis  of  one  eye  to  deviate 
below  that  of  the  other. 

Exophoria,  a  tendency  of  the  visual  axes  outward. 

Esophoria,  a  tendency  of  the  visual  axes  inward. 

Hyperexophoria,  a  tendency  of  the  visual  axis  of  one  eye  to 
deviate  upward  and  outward, 

Hypoexophoria,  a  tendency  of  the  visual  axis  of  one  eye  to 
deviate  downward  and  outward. 

Hyperesophoria,  a  tendency  of  the  visual  axis  of  one  eye  to 
deviate  upward  and  inward, 

Hypoesophoria,  a  tendency  of  the  visual  axis  of  one  eye  to  devi- 
ate downw'ard  and  inward. 

It  must  be  remembered  that,  in  the  functional  anomalies  under 
discussion,  both  eyes  are  involved  and  that  while  the  above 
nomenclature  may  describe  the  symptom,  it  does  not  locate  the 
lesion.  It  is  simply  a  clinical  convenience.  For  instance, 
right  hyperphoria  means  either  that  the  right  elevators  are  too 
strong  for  the  right  depressors,  or  that  the  left  depressors  pre- 
dominate over  the  left  elevators.     In  other  words,   it  simply 


8o  FUNCTIONAL  ANOMALIES. 

signifies  that  one  eye  tends  to  turn  upward  or  the  other  downward, 
without  indicating  which  is  the  faulty  eye. 

To  this  classification  Savage  would  add  cyclophoria,  or  in- 
sufficiency of  the  oblique  muscles;  and  Duane,  hypokinesis, 
deficiency  of  action  of  an  individual  muscle;  and  hyperkinesis, 
excessive  action  of  an  individual  muscle;  and  parakinesis,  irregu- 
lar action  of  an  individual  muscle. 

CONCERNING  PRISMS. 

All  problems  that  deal  with  the  ocular  muscles  turn  more  or 
less  upon  the  use  of  prisms.  It  will  therefore  be  most  profitable 
for  the  student  to  consider  at  this  juncture  the  nature  and  prop- 
erties of  prisms,  so  that  he  may  the  better  appreciate  their  ap- 
plication to  the  diagnosis  and  treatment  of  functional  muscular 
anomalies. 

A  prism  differs  from  a  piece  of  ordinary  plain  glass  only  in 
the  fact  that  its  two  sides  are  inclined  toward  each  other,  forming 
an  edge  or  angle.  Their  surfaces  are  plane  (that  is  to  say  with- 
out any  curvature,  as  is  met  with  in  lenses).     By  reason  of  this 

A' 

"""-^^  Angle 


Fig.  31. — Action  of  a  prism  on  a  beam  of  light.     Dotted  line  indicates  direction 
which  the  projected  beam  talces. 

inclination  of  the  sides  of  the  prism  toward  each  other  a  beam  of 
light  instead  of  passing  through  it  without  change  of  general 
direction  (as  in  the  case  of  window  glass)  is  bent  from  its  course 
toward  the  broad  end  or  base  of  the  prism.  For  the  better  under- 
standing of  the  refractive  properties  of  prisms,  the  student  will 
do  well  to  bear  in  mind  the  law  which  provides  that  as  a  beam 


HETEROPHORIA.  51 

of  light  passes  from  a  rarer  to  a  denser  medium  it  is  bent  toward 
the  perpendicular,  and  that  as  it  passes  from  a  denser  to  a  rarer 
medium  it  is  bent  away  from  the  perpendicular.  Thus,  as  in 
Fig.  31,  if  the  eye  be  placed  at  B  in  the  path  of  the  beam  after  it 
emerges  from  the  prism,  it  will  not  see  the  candle  at  A,  its  true 
position,  but  in  the  direction  of  the  line  BC,  projected  through 
the  prism  along  the  dotted  line  to  A\  Hence  there  is  displace- 
ment of  the  object  in  the  direction  of  the  angle  of  the  prism 
and  on  this  phenomenon  is  based  the  axiom  that  prisms  displace 
the  image  of  an  object  in  the  direction  of  their  edge,  angle  or  apex. 

If,  when  the  eyes  are  directed  toward  an  object  20  feet  or  more 
distant,  a  io°  prism  be  placed,  base  in,  in  front  of  the  right  eye, 
it  so  displaces  the  object  that  the  image  falls  to  the  inner  line  of 
the  fovea,  and,  unless  the  eye  by  rotation  of  its  cornea  temporal- 
ward  effects  a  corresponding  inward  displacement  of  the  fovea 
centralis,  diplopia  is  inevitable.  The  above  elementary  principle 
may  be  illustrated  in  its  application  to  the  prism  test  for  deter- 
mining heterophoria  or  orthophoria. 

In  Fig.  32,  O  is  the  object,  OF  the  ray  proceeding  from  the 
object  to  the  fovea, F,  of  the  right  eye  (R),  and  O'F^  the  ray  from 


Right  retina  (R).  Left  retina  (L). 

Fig.  32. 

the  same  object  which  if  not  interrupted  by  the  prism  would  fall 
upon  F^  in  the  left  eye,  but  a  prism  placed  base  down  before 
that  eye  refracts  the  ray  to  a  portion  of  the  retina  beneath  the 
fovea.  Since  the  lower  half  of  the  retina  refers  its  impressions  to 
the  upper  part  of  the  field,  O*  will  be  projected  above  O  to  O^ 
and  in  a  vertical  line  with  it  in  orthophoria,  or  to  one  or  the  other 
side  of  O  in  lateral  heterophoria.  To  test  for  hyperphoria  or 
hypophoria  the  refracting  prism  is  placed  with  its  base  in,  produc- 
ing insuperable  lateral  diplopia  with  image  of  O  refracted  to  the 
nasal  side  of  the  fovea  of  that  eye  before  which  the  prism  is  placed; 
6 


82  FUNCTIONAL  ANOMALIES. 

if  hyperphoria  exists,  one  image  will  be  seen  higher  or  lower  than 
the  other. 

According  to  the  law  of  projection,  if  an  image  falls  to  the  right 
of  the  fovea  the  object  O  will  be  projected  or  seen  to  the  left 
portion  of  the  field;  if  to  the  left,  to  the  right  portion  of  the  field; 
if  below,  to  the  upper;  and  if  above,  to  the  lower  portion  of  the 
field.  In  Plate  3,  ^  is  the  fundus  of  an  eye  before  which  no 
prism  is  placed;  B,  fundus  before  which  prism  is  placed  base 
down,  I  representing  the  new  position  of  the  image  in  the  lower 
half  of  the  retina;  C,  prism  base  up;  I  displaced  to  the  upper  half 
of  the  retina;  D,  prism  base  in,  displacing  /  to  nasal  half  of  the 
retina;  and  E,  prism  base  out,  displacing  /  to  temporal  half  of 
the  retina. 

The  Relation  Between  Accommodation  and  Convergence. 

If  there  is  one  set  of  phenomena  that  more  than  any  other 
will  help  the  beginner  in  ophthalmology  toward  the  solution  of 
some  of  the  obscure  problems  in  refraction  and  imbalance  of  the 
ocular  muscles,  it  is  the  understanding  of  the  relation  between 
accommodation  and  convergence. 

CONCERNING  ACCOMMODATION. 

Since  the  time  of  Bonders,  it  has  been  known  that  if  an  individ- 
ual who  has  been  shown  (by  the  use  of  a  mydriatic  or  cycloplegic) 
to  be  emmetropic,  fixes  the  gaze  on  an  object  at  infinity,  there 
is  no  accommodation  called  into  play.  If  the  same  individual  be 
requested  to  look  at  proper  sized  print  at  a  distance  of  one  meter, 
it  is  equally  well  known  that  one  diopter  of  accommodation  is 
called  into  play.^ 

Similarly,  to  focus  proper  sized  print  at  a  distance  of  half  a 
meter  (50  centimeters  or  20  inches)  two  diopters  of  accommodation 

*  This  is  proven  by  again  using  a  cycloplegic  in  the  eye  of  such  a  patient,  when  it 
will  be  found  that  he  can  no  longer  read  at  one  meter  the  print  he  read  easily  at  this 
distance  when  the  eye  was  not  atropinized.  To  enable  him  to  read  the  print  at 
this  distance  a  plus  one  diopter  lens  must  be  placed  before  the  eye,  thus  proving  that 
this  was  the  amount  of  accommodation  exercised  before  the  cycloplegic  was  used. 


HETEROPHORIA. 


83 


Fig.  B 


Fig.  A 


i^  =  fovea.     /  =  image.     No  prism.     /  falls  an  F. 


Fig.  C 


Prism  base  down.     I  falls  below  F.  Prism  base  up.     I  falls  above  F. 


Fig.  D 


Fig.  E 


Prism  base  in.  I  falls  to  nasal  side  of  F.    Prism  bsise  out.  I  falls  to  temporalside  olF. 

PLATE  III. 


84 


FUNCTIONAL  ANOMALIES. 


must  be  used  by  the  patient,  and  to  focus  the  same  size  print  at  a 
distance  one  fourth  of  a  meter  (25  centimeters  or.  10  inches)  four 
diopters  of  accommodation  are  demanded.  It  will  be  readily  seen, 
therefore,  that  if  a  patient  who  is  hypermetropic  2  diopters, 
focuses  on  print  at  i  meter's  distance,  he  will  employ  3  diopters 
of  accommodation  (that  is  to  say  the  i  diopter  the  emmetrope 


Fmmefropia         Ni/per/ne/fvpia^ZD  M//opia 


2D. 


Infinitif 


1  Meter    Wiopter 


%  Meter  ^Diopters 


%Meter   i'Dioplers 


_^ 


Z  diopte/s 


IMeterAny/e  oDiop 


ZMeter/lnffles  ^Diop 


4MeterAnffks  SDiop. 


6 


^ 


vj 


/M.J. 


2M.A. 


4M.A.      2Diop 


6 


B»> 


IM.A. 


2M.A. 


■m.A 


6 


Fig.  33- 


would  exercise,  plus  the  2  diopters  the  hypermetrope  exercises 
for  infinity) ;  and  at  one-half  meter's  distance,  the  two  diopter 
hypermetrope  would  utilize  4  diopters  of  accommodation,  while 
at  one-fourth  meter's  distance,  the  2  diopter  hypermetrope 
would  require  6  diopters  of  accommodation  to  see  the  print  clearly. 
In  the  case  of  myopia  of  2  diopters,  there  would  of  course  be  no 


HETEROPHORLA.  85 

effort  at  accommodation  at  infinity,  nor  at  one  meter's  distance. 
Neither  would  there  be  at  one-half  meter's  distance,  for  50  centi- 
meters represent  the  far  point  of  such  an  eye  and  no  accommoda- 
tion is  necessary  to  enable  the  patient  to  read  easily.  At  one- 
fourth  of  a  meter,  however,  for  which  point  the  emmetrope 
accommodates  4  diopters,  the  myope  of  2  diopters  would  naturally 
exercise  but  2  diopters  of  accommodation.  The  accompanying 
diagram  may  help  to  a  clearer  understanding  of  the  principles 
involved  (Fig.  t,t,). 

Concerning  Convergence. 

If  vision  were  effected  by  means  of  one  eye  only,  there  would 
be  no  point  from  beyond  infinity  up  to  within  a  very  short  distance 
from  the  eye  to  which  we  could  not  adjust  the  dioptric  system  of 
that  eye.  But  man  generally  sees  simultaneously  with  two  eyes, 
and  the  direction  that  the  eyes  must  give  to  their  lines  of  fixation 
in  order  that  they  may  be  simultaneously  directed  toward  a  point 
of  fixation  anywhere  inside  of  infinity,  is  called  convergence. 
For  some  years  after  Bonder's  exposition  of  a  precise  method  of 
estimating  accommodation  at  various  distances  it  was  realized  that 
when  an  emmetrope  accommodated  for  an  object  13  inches  or 
35  cm.  distant  from  the  eye,  he  also  converged  his  eyes  on  that 
point,  for  if  he  did  not  he  would  surely  see  double.  But  no 
scheme  of  accurate  and  practical  measurement  of  the  conver- 
gence was  in  vogue  until  Nagel  (Graefe  and  Saemisch  Hand- 
buch,  ist  edition,  Vol.  VI,  Chap.  X)  offered  his  ingenious  unit 
angle  known  as  the  meter-angle.  This  is  now  commonly  desig- 
nated as  MA. 

Convergence  is  in  this  way  easily  expressed.  For  instance  if  a 
patient  bring  his  gaze  from  infinity  to  an  object  i  meter  distant, 
he  is  said  to  have  converged  i  meter  angle.  If  the  object  be  1/2 
meter  (50  cm.)  distant,  he  has  converged  2  meter  angles;  if  1/4 
meter  (25  cm.  or  10  inches)  distant,  he  has  converged  4  meter 
angles.  The  following  table  may  help  to  an  understanding  of  the 
principles  involved. 


86 


FUNCTIONAL  ANOMALIES. 


Accommodation 
diopters 


Convergence 
meter  angles 
or  MA 


Distance  at  which  test; 
are  made 


Infinity. 

I  meter. 
1/2  meter. 
1/4  meter. 


It  will  now  be  readily  observed  that  in  emmetropes  there  is  a 
very  regular  and  close  relation  between  accommodation  and  con- 
vergence. If  such  a  patient  at  i  meter  accommodates  i  diopter, 
he  also  converges  i  meter  angle.  If  at  1/2  meter  he  accommo- 
dates 2  diopters,  he  also  converges  2  meter  angles;  if  at  1/4  meter, 
he  accommodates  4  diopters,  he  converges  4  meter  angles. 

Let  us  assume,  however,  that  the  patient  is  hypermetropic  2 
diopters.  A  new  relation  now  appears,  for  if  such  a  patient 
surveys  an  object  i  meter  distant  he  converges  the  regular  i  meter 
angle,  but  he  accommodates  3  diopters  (the  i  diopter  that  the 
emmetrope  would  employ  plus  the  2  diopters  he  must  need  call 
into  play  even  for  infinity).  If  he  fixes  his  gaze  on  an  object  at 
1/2  meter,  he  converges  2  meter  angles  and  accommodates  4 
diopters;  and  if  the  object  is  at  1/4  of  a  meter  he  converges  4 
meter  angles  and  accommodates  6  diopters  as  shown  in  the  diagram 

(Fig.  33)- 

Let  us  now  assume  for  further  illustration  that  the  patient  is 
myopic  2  diopters.  Another  relation  now  develops.  If  such  a 
patient  views  an  object  i  meter  distant,  he  converges  i  meter 
angle,  but  he  does  not  accommodate  at  all,  as  1/2  meter  (or  50  cm. 
or  20  inches)  is  the  far  point  of  accommodation  in  such  an  eye. 
If  the  object  viewed  is  at  1/2  meter,  the  patient  will  converge 
2  meter  angles,  but  will  still  not  accommodate  at  all,  as  this  is 
the  far  point  of  the  eye.  If  the  object  is  at  1/4  of  a  meter,  the 
patient  will  converge  4  meter  angles  and  accommodate  only 
2  diopters,  as  shown  by  the  diagram  (Fig.  ;^;^). 

The  presence  of  astigmatism  in  combination  with  any  spherical 


HETEROPHORIA.  87 

error  will  naturally  only  complicate  this  relation;  (the  student  who 
wishes  to  go  deeply  into  the  physics,  mathematics  and  psychology 
of  this  relation  is  referred  to  Nagcl's  original  article  {loc.  cit.)  and 
to  Landolt's  voluminous  work  on  the  "Refraction  and  Accommo- 
adtion  of  the  Eye,"  translated  by  Culver).  Enough  has  been  said, 
however,  to  show  that  nature  establishes  for  each  person  some 
manner  of  relation  between  accommodation  and  convergence  if 
they  enjoy  binocular  single  vision.  It  will  be  found  to  be  a  most 
elastic  relation  subject  to  many  changes  and  more  or  less  adapt- 
able to  varying  states  of  refraction  in  the  same  individual.  It  is 
well  for  the  student  to  realize  this  point,  that  //  is  the  breaking  in 
upon  this  relation  {peculiar  to  each  individual)  that  produces 
much  of  the  discomfort  complained  of  by  most  patients  when 
they  first  put  on  glasses.  If  they  have  been  hypermetropic  (say 
2  diopters)  when  their  glasses  are  first  worn  they  naturally 
need  to  use  less  accommodation  and  therefore  there  is  less  impulse 
to  convergence,  so  that  a  certain  amount  of  confusion  is  thrown 
into  the  completed  visual  act.  In  some  individuals  who  do  not 
readily  acquire  newly  established  coordinations  and  coordinate 
relations,  this  period  of  discomfort  may  extend  into  weeks  and 
weeks,  in  which  case  it  may  become  necessary  to  cut  down  the 
strength  of  the  plus  glass  ordered  and  thus  break  in  less  on  the 
relation  between  accommodation  and  convergence  which  had 
existed  prior  to  putting  on  glasses.  In  others  but  a  few  days 
suffice  for  the  establishment  of  new  relations  and  they  quickly 
become  used  to  their  glasses.  The  same  is  true  in  myopia  and 
is  even  truer  in  astigmatism.  So  that  unless  the  ophthalmologist 
is  by  nature  a  persuader  of  people,  he  will  have  much  difllculty 
in  carrying  many  of  his  patients  through  this  period  that  is  so  try- 
ing to  them,  unless  he  bears  in  mind  all  the  time  the  intimacy  of 
this  relation  and  its  importance  in  making  the  final  judgment 
as  to  what  lenses  shall  be  prescribed;  it  will  suffice  to 
say  that  it  is  the  experience  of  the  authors  that  full  cor- 
rections in  hypermetropes  are  not  often  well  borne,  this  in 
spite  of  the  fact  that  on  theoretic  grounds  the  full  mydriatic 
correction   should   be   given,  thus  establishing  that  relation  be- 


88  FUNCTIONAL   ANOMALIES. 

tween  accommodation  and  convergence  which  normally  obtains 
in  the  emmetrope.  As  has  been  already  said,  however,  if  the 
intrusion  into  the  patient's  previously  established  relation  be- 
tween accommodation  and  convergence  is  made  too  great  and 
too  abrupt  (as  it  generally  is  by  ordering  the  full  corrections) 
the  patient  will  finally  conclude  that  the  glasses  are  'Hoo  strong'^ 
and  refuse  point  blank,  in  many  instances,  to  continue  any  longer 
with  them. 

METHODS  OF  DIAGNOSIS. 

The  purpose  of  the  various  tests  for  the  determination  of 
muscular  imbalance  is  to  so  affect  the  retinal  image  of  one  eye, 
by  alterations  in  color,  shape,  or  position,  that  the  fusion-impulse 
will  no  longer  be  exercised,  and  that  the  tendency  to  deviation 
will  become  changed  from  a  latent  into  a  manifest  one. 

These   tests  may  be   arranged  in   three   groups  as   follows: 

1.  Those  that  displace  one  image.  (Displacement  or  diplopia 
tests.) 

2.  Those  that  distort  one  image. 

3.  Those  that  neither  displace  nor  distort  either  image. 

I.  Diplopia  (or  Displacement)  Tests. 

The  classic  test  first  suggested  by  v.  Graefe  is  the  prism  test. 
A  prism  of  8  degrees,  with  its  base  down,  or  up,  is  too  strong  to  be 
overcome  by  the  muscles  it  antagonizes,  and  will  produce  insuper- 
able diplopia.  For  instance,  to  test  lateral  equilibrium,  a  prism  of 
8  degrees  held  base  down  before  the  right  eye,  with  its  base-apex 
line  exactly  vertical,  will  so  refract  the  rays  entering  that  eye 
that  they  will  fall  upon  the  lower  portion  of  the  retina,  and  a 
false  image  of  the  light  will  be  projected  into  the  upper  part  of 
the  visual  field.  In  orthophoria,  the  true  (or  lower)  and  the 
false  (or  upper)  lights  are  in  a  vertical  line.  In  esophoria,  the 
upper  image  will  be  to  the  right  of  an  imaginary  line  running 
vertically  through  the  lower  or  true  light.  The  prism  displaces 
the  retinal  image  of  the  light  to  the  lower  and  (if  the  eye  is  turned 


HETEROPHORIA.  89 

in)  also  to  the  inner  half  of  the  right  retina;  it  is  therefore  projected, 
or  seen,  up  and  to  the  right.  In  exophoria,  with  the  prism  in  the 
same  position  before  the  right  eye,  the  false  image  will  be  above 
and  to  the  left.  The  distance  that  the  upper  light  is  to  the  right 
or  left  of  the  imaginary  vertical  line  drawn  through  the  lower  one, 
is  the  linear  measure  of  the  degree  of  the  deviation.  The  prism 
(with  its  base  out  for  esophoria,  in  for  exophoria)  necessary  to 
move  the  upper  image  until  it  is  directly  over  the  lower  one  will 
be  the  angular  measurement  of  the  deviation.  The  principle  of 
this  test  is  exactly  the  same  as  that  of  all  others — namely,  the  de- 
struction of  the  unconscious  fusion-impulse.  The  individual 
seeing  two  images  of  the  same  object  simultaneously  accepts 
the  impression  that  the  two  images  represent  two  objects. 
Fusion  having  been  thus  destroyed,  the  deviation  tendencyhecom.es 
an  actual  turning,  and  the  eyes  assume  that  position  which  is 
most  restful  for  them  and  to  which  they  are  impelled  by  the  condi- 
tions present  in  the  individual  case.  The  prism  commonly  em- 
ployed is  of  8  to  ID  degrees.  This  strength  is  sufficient,  not  only  to 
produce  insuperable  diplopia,  but  to  separate  the  false  from  the 
true  image  by  an  interval  great  enough  to  allow  slight  deviation 
tendencies  to  cause  a  lateral  displacement  of  the  images  that  is 
instantly  perceptible.  Two  serious  errors  arise  when  higher 
degree  prisms  are  used — namely,  the  false  image  is  refracted  to  a 
point  on  the  retina  so  far  removed  from  the  real  fovea  that  the 
findings  may  not  accurately  represent  the  anomaly,  and  the 
slightest  turning  of  the  prism  from  its  axis  will  vitiate  the  result 
by  producing  artificial  heterophoria.  In  Stevens'  phorometer, 
instead  of  a  single  prism  of  8  degrees  before  one  eye,  the  effect 
is  divided  between  the  two  eyes  by  means  of  two  prisms  of  4 
degrees  each  which  are  held  in  a  frame  that  can  be  rotated  to 
test  either  the  horizontal  or  the  vertical  tensions.  (See  Fig.  34.) 
The  instrument  is  convenient,  because  both  vertical  and  lateral 
imbalance  can  be  determined  by  simply  revolving  the  test-prisms 
into  the  horizontal  or  the  vertical  meridian.  A  total  of  8  degrees 
is  selected,  because,  at  the  distance  at  which  these  prisms  are 
placed  from  the  patients'   eyes,  muscles  of  average  diverging 


90  FUNCTIONAL  ANOMALIES. 

power  cannot  fuse  the  double  images.  With  the  instrument 
fixed  to  test  the  lateral  muscles,  two  images  separated  vertically 
will  be  seen.  In  orthophoria  these  images  are  directly  in  a  verti- 
cal line,  for  although  single  vision  has  been  destroyed,  no  hitherto 
latent  tendency  to  turn  the  eyes  in  or  out  has  become  manifest, 
and  the  lateral  muscles  are  said  to  be  in  equilibrium.  In  ex- 
ophoria  or  esophoria,  one  light,  instead  of  being  exactly  above 
the  other,  will  assume  a  position  a  little  to  the  right  or  left,  be- 
cause the  eyes  are  now  free  to  respond  to  the  influence  of  the 
relatively  stronger  act  (convergence  in  esophoria  and  divergence 


Fig.  34. — Steven's  Phorometer. 

in  exophoria.)  The  degree  of  prism  now  necessary  to  bring  the 
upper  image  directly  over  the  lower  one,  is  the  measure  of  the 
deviation.  This  is  accomplished  by  simply  rotating  the  lever 
of  the  Stevens  instrument  until  the  two  images  are  in  exact  vertical 
alignment  when  the  muscle's  status  can  be  immediately  read  off 
from  the  scale  provided  for  this  purpose.  The  lever  is  then  car- 
ried around  exactly  90  degrees  when  the  test  is  quite  as  quickly 
made  for  the  state  of  the  vertical  muscles  (by  means  of  lateral 
diplopia)  and  the  reading  taken  at  once  from  the  scale.  It  must 
be  remembered  we  are  dealing,  not  with  one,  but  with  both  eyes. 
For  instance,  in  esophoria  we  study  not  one  internus,  but  the  power 
of  convergence  as  contrasted  with  the  power  of  divergence,  and 
by  this  test  we  determine,  in  esophoria,  that  convergence  is 
abnormally  and  relatively  strong. 


HETEROPHORIA.  9 1 

The  Maddox  double  prism  consists  of  two  4-degree  prisms, 
bases  together,  fitted  into  an  ordinary  test  glass  cell  and  held 
before  one  eye  (Fig.  35).  It  will  cause  the  light  as  seen  by  that 
eye  to  be  doubled  (monocular  diplopia).  If  now  the  other  eye 
be  uncovered,  a  third,  which   is  the  true  image,  will  appear 


Fig.  35. — Maddox  double  prism. 


midway  between  the  two  and  directly  on  a  line  with  them  in  or- 
thophoria (Fig.  36).  I.  With  the  double  prism  placed  in  the 
trial  frame  two  images  are  seen  in  the  vertical  meridian.  The 
true,  or  middle  image,  will  be  out  of  line,  to  the  right  or  left,  ac- 
cording as  there  is  exophoria  or  esophoria.     2.  Let  the  two  images 


Fig.  36. — Effect  of  a  double  prism  on  a  beam  of  light.     (Maddox.) 

be  on  a  horizontal  line,  then  the  true  image  will  be  above  or  below 
this  line  in  hyperphoria.  The  test  is  facilitated  when  the  double 
prism  is  ground  in  red  instead  of  clear  glass.  Another  applica- 
tion can  be  made  of  this  prism  by  observing  whether  the  middle 
or  true  image  is  equidistant  from  the  two  false  (red)  ones.     If  not. 


92  FUNCTIONAL   ANOMALIES. 

the  prism  necessary  to  restore  it  to  the  orthophoria  middle  position 
will  be  the  measure  of  both  the  kind  and  the  degree  of  the  hetero- 
phoria.  This  prism  is  usually  applied  to  investigating  the 
tensions  of  the  oblique  muscles  by  having  the  patient  survey  a 
line  on  a  card.  If  they  are  faulty  in  action,  the  middle  line 
is  tilted  up  or  down  at  the  right  or  left. 

The  Cobalt  Test.^A  glass  stained  with  cobalt  oxide  and 
ground  to  fit  the  trial  frame  has  the  power  of  intercepting  all  the 
rays  of  the  spectrum  excepting  the  blue  and  the  red.  The  image 
seen  by  the  eye  before  which  the  cobalt  glass  is  placed  will  be  much 
smaller  than  the  real  image,  and  will  have  a  red  center  with  a 
blue  halo,  or  a  blue  center  with  a  red  halo;  the  former  in  myopia, 
the  latter  in  hypermetropia  and  emmetropia.  This  test  has  the 
advantage  over  all  the  others  in  that  it  does  not  refract  the  rays 
before  they  enter  the  eye,  and  in  all  cases  the  rays  pass  through 
parallel  and  are  focused  on  the  fovea.  Hence,  if  deviation  be 
discovered  it  must  be  the  result  of  muscular  insufficiency  and  not 
due  to  inadequacy  of  the  method  of  diagnosis.  The  method  is 
valuable  only  in  cases  of  2  degrees  or  more  of  vertical  and  4 
degrees  or  more  of  horizontal  imbalance.  Fusion  power  is 
largely  destroyed,  and  in  the  presence  of  any  considerable  hetero- 
phoria  the  patient  will  see  two  images,  one  the  clear  or  natural 
colored  light,  the  other  the  smaller  blue-red  light.  In  orthophoria 
both  images  fall  upon  the  fovea  and  the  composite  light  will  then 
be  the  clear  light  tinged  with  red  and  blue.  In  heterophoria 
the  cobalt  image  will  be  separated  from  the  natural  image  ac- 
cording to  the  kind  and  degree  of  the  defect.  In  esophoria,  for 
example,  it  will  be  on  the  side  of  the  eye  covered  by  the  cobalt 
glass  and  on  a  level  with  the  true  light,  the  interval  between  them 
depending,  as  in  other  instances,  upon  the  degree  of  the  defect. 
In  our  opinion,  diplopia  tests  (with  the  exception  of  the  cobalt 
test)  do  not  always  indicate  the  true  condition,  for  the  reason 
that  the  foveal  region  in  each  retina  is  not  considered,  but 
rather  the  fovea  in  one  eye  and  a  point  outside  the  fovea  in  the 
other  eye.  Hence,  while  the  fusion-impulse  is  destroyed  (which 
is  necessary),  we  are  expecting  identical  muscle-action  as  the 


HETEROPHORIA. 


93 


result  of  stimulation  of  different  retinal  areas  in  the  two  eyes. 
We  have  found  that  such  tests  are  likely  to  show  exophoria  to  be 
more  frequent  than  esophoria,  and  have  often  found  a  positive 
contradiction  between  the  results  of  these  tests  and  those  obtained 
by  the  use  of  the  Maddox  rod  and  other  tests. 

The  Convex  SpJicrical. — A  convex  glass  of  a  strength  of  15  to 
20  diopters,  covered  in  all  parts  excepting  its  center,  is  placed 
before  one  eye  in  the  trial  frame.  The  image  seen  by  that  eye 
assumes  the  shape  of  a  large  blur  upon  the  fovea  and  the  adjoining 
retina.  In  orthophoria,  the  clear  light  seen  by  the  uncovered 
eye  will  be  situated  in  the  center  of  the  blurred  image  of  the 
covered  eye  (Fig.  37).     In  heterophoria  of  low  grade,  the  clear 


Orthophoria  Heterophoria. 

Fig.  37. — The  convex  spherical  test. 


image  appears  on  the  outskirts  of  the  blurred  image,  and  in 
the  higher  grades  will  be  seen  entirely  outside  of  it.  The  space 
between  the  true  light  and  the  center  of  the  blurred  area  is 
the  linear  measure  of  the  deviation,  and  the  prism  required 
to  refract  the  clear  image  into  the  center  of  the  blurred  one  will 
be  the  prism  measurement  of  the  heterophoria.  This  test  can  be 
accurate  only  when  but  a  small  portion  of  the  exact  center  of  the 
lens  is  left  clear,  because  rays  of  light  passing  through  it  at  any  con- 
siderable distance  from  the  axial  ray  are  refracted  away  from  the 
fovea,  and  should  an  excentral  portion  of  the  lens  be  brought 
opposite  to  the  pupil,  the  image  of  the  light  will  not  fall  on  the 


94 


FUNCTIONAL   ANOMALIES. 


fovea.  Hence,  the  method  is  open  to  the  objection  of  the 
prism  test  and  to  the  additional  one  that  unless  extreme  care 
is  experienced  apparent  deviation  may  be  created  by  faulty  use 
of  the  test. 


2.  Distorting  Tests. 

The  Maddox  Rod  (Fig.  38).— This  consists  essentially  of  a 
rod  of  glass  conveniently  adjusted  in  a  disc  to  fit  the  trial  frame. 
When  light  is  refracted  by  a  glass  rod,  a  luminous  point  becomes 
a  line  or  streak,  since  the  rod  is  nothing  more  than  a  strong 
cylinder.     As  a  glass  rod  refracts  rays  of  light  opposite  to  its  axis 


Maddox  simple  rod. 


Fig.  38. 


Maddox  compound  rod. 


the  eye  will  see  a  streak  of  light  in  the  reverse  meridian  to  that  in 
w^hich  its  axis  is  placed.  Hence,  if  the  rod  is  placed  vertically 
before  one  eye,  the  image  of  the  light  seen  by  that  eye  is  a  hori- 
zontal streak;  if  placed  horizontally  the  image  is  a  vertical 
streak.  In  orthophoria  the  candle-flame  or  point  of  light  6 
meters  distant  to  which  the  patient's  gaze  is  directed  is  seen 
as  a  streak  by  the  eye  before  which  the  rod  is  placed,  the  streak 
passing  through  the  unaltered  flame  seen  by  the  other  eye.  In 
heterophoria  the  streak  is  seen  either  to  the  left,  to  the  right, 
above  or  below,  according  to  the  nature  of  the  defect.  In 
esophoria  the  streak  is  on  the  same  side  as  the  eye  which  sees 


HETEROPHORIA. 


95 


it.  For  example,  a  Maddox  rod  so  placed  before  the  right  eye 
that  the  streak  is  vertical  will  be  seen  to  the  right  of  the  candle- 
flame.  In  exophoria  the  conditions  are  reversed,  the  streak 
under  the  same  conditions  being  seen  to  the  left  of  the  flame. 
In  hyperphoria,  the  phenomenon  is  a  little  more  confusing. 
For  instance,  in  right  hyperphoria,  if  the  rod  is  placed  be- 
fore the  right  eye,  the  streak  v^ill  be  seen  belov^  the  flame; 
if  it  is  placed  before  the  left  eye  it  will  be  seen  above  the  flame; 
in  left  hyperphoria,  the  rod  before  the  left  eye  will  produce  a 
streak  below  the  flame;  before  the  right  eye,  a  streak  above  the 
flame.  The  prism  necessary  to  change  the  position  of  the  streak 
from  its  faulty  position  into  the  light  (the  orthophoria  position) 


6. 


B- 


/ 


Fig.  39. — Maddox  rod  before  right  eye.     a,  lateral  balance;  h.  esophoria;  c,  exo- 
phoria; d,  vertical  balance;  e,  right  hyperphoria;  /,  left  hyperphoria. 

is  the  measure  of  the  heterophoria.  This  instrument  is  simple, 
inexpensive,  accurate  and  trustworthy,  especially  in  its  latest 
form  of  the  compound  rod,  and  exceedingly  useful  when  the 
student  is  familiar  with  the  law  of  projection.  The  advantage 
of  the  latter  over  the  simple  rod  is  that  no  special  care  in  its 
adjustment  is  necessary;  with  the  simple  rod  it  is  essential  to 
accuracy  that  the  rod  shall  be  in  line  with  the  visual  axis. 
While  the  image  is  greatly  distorted  by  this  test,  yet  the  foveal 
region  of  the  retina  is  included  in  the  site  of  the  image,  and  we 
are  studying  the  relations  of  the  two  foveas  to  each  other,  and 
not,  as  in    the    prism    test,  the  relation  of    one   fovea  with  a 


96  FUNCTIONAL  ANOMALIES. 

circummacular  portion  of  the  other  retina.  By  the  rod  test  we 
find  esophoria  more  common  than  exophoria,  and  from  the  study 
of  other  conditions,  such  as  the  refraction,  are  led  to  believe 
that  this  is  correct.  For  the  relative  positions  of  the  streak  and 
light  in  the  various  muscular  states,  see  Fig.  39. 
3.  Tests  which  Neither  Displace  nor  Distort  Either  Image. 
The  Cover  Test. — The  patient  is  requested,  while  standing  in  a 
good  light,  to  gaze  at  a  small  object  20  feet  or  more  distant. 
The  eyes  are  screened  alternately,  thus  breaking  up  fusion.  As 
the  cover  is  carried  from  one  to  the  other  eye,  no  movement  will 
be  seen  in  orthophoria  because  the  visual  axes  are  parallel,  but 
an  excursion  will  be  noticed  in  heterophoria.  As  the  cover  is 
carried  to  and  fro,  if  marked  esophoria  be  present,  the  eye  un- 
covered will  move  in  a  direction  exactly  contrary  to  the  movement 
of  the  cover;  e.g.,\i  the  cover  is  carried  from  the  left  to  the  right,  the 
left  eye  will  move  to  the  left,  and  vice  versa;  and  the  prism,  base 
ontf  before  either  eye  that  stops  this  movement  will  be  the  ap- 
proximate measure  of  the  heterophoria.  The  method  is  appli- 
cable to  all  high-grade  heterophorias  of  whatsoever  kind,  as  well 
as  the  prism  measure  of  strabismus.  It  does  not  consume  more 
than  thirty  seconds  in  its  application  and  should  never  be  omitted 
from  the  study  of  any  case. 


■;.HI'LJI:U1-H^J=»  ».I.I.I'»CTa: 


Fig.  40. — Cover  for  cover  test  and  parallax  test. 

The  Parallax  Test. — The  preceding  or  cover  test  is  entirely 
objective.  If,  however,  as  the  cover  is  carried  repeatedly  from  one 
to  the  other  eye  the  patient  is  asked  to  state  whether  the  object 
surveyed  seems  to  jump  from  side  to  side  or  up  and  down,  the 
test  then  becomes  subjective  and  is  known  as  the  parallax  test. 
The  slightest  apparent  movement  of  the  object  will,  after  a  few 
trials,  be  remarked  by  the  patient,  who  accurately  describes  the 


HETEROPHORIA.  97 

direction  and  extent  of  the  movement.  In  orthophoria  naturally 
the  object  will  appear  perfectly  stationary.  If  the  object  moves 
in  the  same  direction  as  the  cover  is  carried,  exophoria,  and  if 
in  the  opposite  direction  esophoria,  is  present.  If  the  object 
appears  to  shift  downward  when  the  right  eye  is  uncovered  there 
is  right  hyperphoria,  and  if  the  reverse,  left  hyperphoria.  This 
movement  may  be  completely  controlled  by  prisms,  and  the 
degree  of  prism  which  stops  the  movement  is  the  measure  of  the 
heterophoria.  This  test  is  susceptible  of  extreme  delicacy, 
deviations  as  slight  as  one-eighth  of  a  degree  being  measurable 
in  some  instances.  Fig.  40  illustrates  a  convenient  cover  with 
handle  for  use  in  this  and  the  preceding  test. 

In  general  terms  it  may  be  said  that  those  tests  which  are  at 
the  same  time  the  most  accurate,  the  simplest,  and  require  the 
least  apparatus,  are  the  ones  most  likely  to  lead  the  beginner  to  the 
surest  results.  For  this  reason  the  Maddox  rod  (compound)  and 
the  cover  and  parallax  test  are  trustworthy,  although  the  phoro- 
meter  has  many  warm  advocates.  The  cover  and  the  parallax 
test  have  the  great  advantage  of  finding  the  eyes  just  as  they  are 
and  *as  the  patient  uses  them  all  day  long  and  is  least  likely  to 
create  any  factors  of  error.  On  the  other  hand,  the  phorometer  is 
easy  and  quick  of  application  and  very  helpful  to  the  novice  in 
indicating  for  him  the  kind  and  amount  of  deviation  present. 

Tests  for  the  Reading  Distance. 

The  Dot  and  Line  Test. — The  principle  is  exactly  that  described 
for  the  prism  test  at  20  feet.  It  was  devised  by  v.  Graefe 
for  testing  insufficiency  of  the  interni  only.  A  prism  of 
8  degrees  is  placed  base  down,  before  one  eye.  The 
patient  gazes  at  a  small  black  dot,  through  which  a  line 
is  drawn,  on  a  card  held  at  the  ordinary  reading  distance 
(Fig.  41).  If  the  prism  is  placed  base  down  before  the 
right  eye,  the  two  dots  will  be  seen  on  the  same  line  in 
orthophoria.  In  lateral  insufficiency  both  dot  and  line 
will  be  doubled,  the  upper  belonging  to  the  right  eye.  The 
false  image  will  be  to  the  right  (esophoria)  or  to  the  left  ^i^.  41. 
7 


98  FUNCTIONAL  ANOMALIES. 

(exophoria)  according  to  the  lateral  deviation.  In  hyperphoria, 
with  the  test-card  and  the  prism  changed  from  the  vertical  to  the 
horizontal  position,  the  false  dot  and  line  will  be  above  or  below 
the  true  dot  and  line.  In  balance  of  the  vertical  muscles  the 
false  and  true  dots  will  be  on  the  same  vertical  line.  In  our 
judgment,  the  dot  alone  forms  a  superior  test,  since  the  line 
maintains,  in  part  at  least,  the  desire  for  fusion  and  serves,  in  a 
measure,  to  prevent  independent  movement  of  either  eye.  A 
small  printed  word  may  be  similarly  employed. 

The  Maddox  test  for  the  reading  distance,  based  also  upon 
prism  displacement,  provides  a  scale  for  the  measurement  of 
the  angular  deviation  without  other  means  (Fig.  42). 


fo's°  8°  T  e's"  4'  i 


T 


10' 9'  8'  7'  G'  S' t' S' Z'  7 


r  z'3'<f  S'e  Ts's'ic 


Fig.  42. — Maddox  test  for  the  near  point. 

Maddox  Rod  and  Miniature  Light.- — In  our  later  experience  we 
have  come  to  rely  almost  wholly  on  the  Maddox  compound  rod 
and  the  small  electric  light  commonly  used  in  the  electric  ophthal- 
moscope. The  patient  holds  the  light  at  his  usual  reading  or 
occupation  distance  and  the  muscle  balance  at  that  point  is  just 
as  quickly,  accurately  and  easily  secured  as  in  the  test  for  infinity. 
Moreover,  the  moment  the  test  for  the  reading  distance  muscle 
status  is  completed,  the  Maddox  rod  may  be  removed  from  the 
trial  frame  and  the  little  light  used  as  an  ophthalmodynamometer 
(as  described  on  page  107),  which  information  should  always  be 
elicited  in  cases  with  obscure  symptoms. 

MUSCULO-DYNAMICS. 

In  making  up  our  minds  as  to  the  advisability  of  either  optical 
or  surgical  treatment  of  heterophoria  the  relations  of  the  defective 
muscles  and  their  synergists  to  the  antagonistic  muscles  must  be 
given  due  weight.     No  tests  for  muscular  coordination  are  com- 


HETEROPHORM. 


99 


plete  that  do  not  take  account  of  the  relation  to  each  other  of 
the  various  conjugate  rotations  of  the  globes,  the  practical  de- 
termination of  which  is  based  upon  the  ability  of  the  muscles  to 
overcome  prisms  base  up,  down,  in,  or  out,  while  both  eyes  are 
fixed  on  a  small  object  at  6  meters  or  at  the  ordinary  reading 
distance.  For  instance  it  is  not  enough  to  say  a  patient  has  3 
degrees  of  exophoria  to  induce  treatment  for  exophoria,  but  this 
diagnosis  should  be  confirmed  by  showing  a  corresponding  change 
from  the  normal  relations  of  abduction  and  adduction;  that  is, 
a  diminished  prism  convergence  and  an  increased  prism  diver- 
gence. In  hyperphoria  the  diagnosis  should  be  substantiated 
by  an  increased  supra-duction  or  corresponding  decrease  of  the 
infra-duction.  Thus  right  hyperphoria  of  2  degrees  would  in- 
dicate that  right  supra-duction  was  stronger  by  that  amount  than 
right  infra-duction. 

If  the  prism  which  is  placed  before  the  eye  is  not  too  strong  to 
overcome  the  power  of  fusion  (in  other  w^ords,  to  destroy  bin- 
ocular vision)  the  eye  before  which  it 
is  placed  will  be  so  rotated  that  the 
fovea  will  be  moved  from  its  original 
position  to  that  occupied  by  the  image. 
This  faculty  of  setting  aside  by  rota- 
tion the  transient  diplopia  thus  in- 
duced is  known  as  the  ability  to 
overcome  prisms,  or  the  prism  rota- 
tion, or  the  deviation  power  of  the 
muscles.  The  student  must  not  con- 
fuse prism  rotation  in  the  sense  just 
mentioned  wdth  the  arc  rotations  of 
the  eye;  for  instance,  the  abductors 
will  normally  overcome  but  8  to  10  degrees  of  prism  base-in  at  6 
meters  (external  prism-rotation,  abduction,  or  prism  divergence) 
whereas  the  eye  can  be  rotated  or  the  gaze  directed  45  to  50 
degrees  from  the  primary  position  (arc  rotation  or  version). 

When  the  prism  is  first  interposed  the  right  eye  sees  the  image 
at  A^  (Fig.  43),  but  in  response  to  the  fusion  impulse  it  is  rotated 


Fig.  43- 


]00 


FUNCTIONAL   ANOMALIES. 


outward  so  that  the  fovea  is  moved  from  F  to  F\  where  the  image 

may  fall  directly  upon  it  and  binocular  vision  be  thus  restored. 

The  limits  to  the  power  of  rotation  of  the  eyeballs  are  fairly 

well  defined  in  the  various  meridians  as  measured  by  the  prisms 

that  they  overcome.  Beyond  these 
limits  fusion  is  no  longer  possible  and 
diplopia  ensues,  hence  the  following 
terms: 

Abduction  or  prism-divergence. 
Adduction  or  prism-convergence. 
Supraduction  or  vertical  divergence. 
Infraduction  or  vertical  divergence. 
To  test  abduction  the  prisms  are 
placed  base  in  before  either  or  both 
eyes. 

To  test  adduction  the  prisms  are 
placed  base  out  before  either  or  both 
eyes. 

To  test  supraduction  the  prisms  are 
placed  base  down. 

To  test  infraduction  the  prisms  are 
placed  base  up. 

Formerly  prisms  were  made  square, 
but  they  are  now  so  shaped  that  they 
may  be  fitted  into  the  cell  of  an  ordi- 
nary trial  frame. 

It  is  the  general  custom  to  have  the 
patient  seated  about  6  meters  away 
from  a  small  electric  light  or  lighted 
candle,  directing  him  to  fix  his  gaze 
on  the  light.  Prisms  are  then  inter- 
posed with  their  bases  up,  down,  in, 
or  out  respectively  until  permanent  diplopia  is  produced.  The 
highest  prism  that  can  be  overcome,  or  with  which  single  vision 
is  still  possible,  is  the  measure  of  the  prism  rotation  of  the  eyes 
— e.g.,  if  the  eyes  overcome  an  8  degree  prism,  base  in,  but  not 


Fig.  45. — Gould's  prism  battery. 


HETEROPHORIA.  lOI 

a  9  degree,  abduction  equals  8  degrees;  if  a  15  degree  prism, 
base  aul,  but  not  a  16  degree,  adduction  equals  15  degrees;  if  a 
2  degree  prism,  base  up  or  doiem  before  the  right  eye,  but  not 
a  2  I  /2  degree,  right  supraduction  or  infraduction  respectively 
of  2  degrees  is  shown.  It  should  be  borne  in  mind  that  a  prism 
with  its  base  down  before  one  eye  is  equivalent  in  its  action  to 
the  same  degree  of  prism  with  its  base  up  before  the  other  eye. 

Various  devices  are  employed  by  different  workers  for  the 
estimation  of  the  ductional  powers  of  the  ocular  muscles,  principal 
among  which  are  single  prisms,  the  prism  battery,  Risley's 
rotary  prism,  Jackson's  rotary  prism,  and  Landolt's  ophthalmo- 
dynamometer. The  method  just  described,  upon  the  princi- 
ple of  which  most  of  the  others  depend,  is  that  by  the  use  of 
the  single  prisms.  A  more  convenient  method  of  interposing 
one  prism  after  another  in  testing  the  ocular  rotations  is  by 
the  prism-battery,  first  suggested  by  Noyes  and  later  modified 
and  warmly  advocated  by  Gould  (Fig.  44). 

The  series  begins  with  i  -degree  prisms  on  each  side,  and  increases 
by  integers  of  i  degree  to  20  degrees;  thus  by  steps  of  2  degrees 
each,  all  degrees  of  abduction  and  adduction  from  2  degrees 


Fig.  45. — Risley's  rotary  prism. 

to  40  degrees  may  be  measured.  "  Each  battery  is  revolved  at 
pleasure,  being  fixed  by  a  pivot  mechanism  above  and  below,  and 
temporarily  held  in  the  position  desired,  by  clutches  at  the  sides. 
To  measure  adduction  each  battery  is  placed  bases  out;  to  measure 
abduction,  each  battery  is  revolved  so  that  the  bases  are  in.  The 
open  central  space  permits  the  lenses  to  be  brought  close  to  the 


I02 


FUNCTIONAL   ANOMALIES. 


eyes  without  interfering  with  the  patient's  nose."  This  instru- 
ment is  applied  only  to  the  lateral  rotations.  For  measuring  the 
vertical  rotations,  we  would  suggest  a  similar  battery  (single) 
carrying  weak  prisms  (from  i  /4  degree  to  5  degree)  bases  up  or 
down.  By  reversing  the  battery  both  supra-  and  infraduction 
could  thus  be  readily  and  accurately  determined.  However,  all 
these  requirements  and  necessities  are  beautifully  met  in  what  is 
known  as  the  "prism  mobile,"  on  the  principle  first  suggested  by 
Sir  John  Herschel,  who  showed  how  by  placing  two  prisms  in 
opposition  and  rotating  them  in  opposite  directions,  we  can  pro- 
duce the  effect  of  a  single  increasing  prism.  By  far  the  neatest 
application  of  Herschel's  idea  is  that  of  the  Rotary  Prism  designed 
by  Risley  (Fig.  45),  to  be  fitted  into  an  ordinary  trial  frame. 
On  turning  the  little  mill-edged  screw,  the  two 
prisms,  of  15  degrees  each,  rotate  in  opposite 
directions,  the  strength  of  the  resultant  prism 
showing  on  a  graduated  scale  engraved  on  the 


Fig.  46. — Well's 
hand  phorometer  ad- 
justed for  testing  the 
lateral  muscle  balance. 


Fig.  46a. — ^^'el^s  hand  phorometer 
adjusted  for  testing  the  vertical  muscle 
balance. 


blackened  front  of  the  containing  cell.  However,  by  occasioning 
chromatic  aberration  and  prismatic  astigmatism,  all  rotary 
prisms  share  the  disadvantage  of  lowering  the  visual  acuity  in 
one  eye  only,  and  thus  the  desire  for  single  vision  is  more  inter- 
fered with  than  if  the  prism  effect  were  divided  between  both  eyes. 
Maddox  has  therefore  suggested  an  apparatus  in  which  one  prism 
revolves  before  each  eye.  It  is  practically  the  same  as  the 
prism  arrangement  in  Stevens'  phorometer,  and  is  useful  only 
in  measuring  lateral  rotations.  A  similar  instrument  for  measur- 
ing vertical  rotations  could  easily  be  devised  by  having  the  prisms 


HETEROPHORIA.  IO3 

fitted  into  Maddox'  device,  bases  in,  and  then  rotating  them 
in  opposite  directions.  Wells  ofifers  a  very  handy  pocket  phoro- 
meter  for  clinical  and  bedside  use  (Fig.  46).  To  produce  more 
delicate  results  in  the  lower  prismatic  powers,  Jackson  employs 
in  his  rotary  prism  three  prisms,  one  15  degree  stationary  prism 
and  two  rotating  ones  of  7  1/2  degrees  each. 

MEASURE  OF  DUCTION  POWERS. 

Of  the  four  principal  prism  rotations,  above  mentioned  three 
of  them — namely,  abduction,  supraduction,  and  infraduction — 
are  fairly  constant  in  quantity,  and  authorities  agree  more  or 
less  in  fixing  the  power  of: 

Abduction .  .   from  6  to  8  degrees. 

Supraduction from  2  to  3  degrees. 

Infraduction from  2  to  3  degrees. ' 

Much  depends  on  the  method  used  in  the  determination. 
The  above  figures  are  those  furnished  by  single  or  separate 
prisms  held  before  the  eye  one  after  another.  Rotary  prisms, 
especially  as  employed  by  Maddox,  or  any  similar  apparatus  of 
graduated  increment,  indicate  somewhat  higher  average  powers 
of  rotation,  viz.: 

Abduction 8  to  10  degrees. 

Supraduction 3  to    4  degrees. 

Infraduction 3  to    4  degrees. 

The  fact  seems  to  stand  that  if,  at  the  first  trial  of  abduction,  it 
is  found  to  equal  7  degrees,  there  will  be  little  if  any  variation  in 
its  degree,  no  matter  how  often  it  is  tried  on  the  same  day  or  suc- 
ceeding days,  provided  only  that  the  same  method  is  used  each 
time.  The  same  relative  constancy  is  found  in  supraduction 
and  infraduction.  Not  so,  however,  with  adduction,  which  by 
its  variation  from  day  to  day,  and  even  from  hour  to  hour  in  some 
cases,  has  thrown  much  confusion  into  the  subject  of  muscular 

'  These  figures  hold  for  20  ft.  or  more  only.  For  any  distance  less  than  20  ft. 
abduction  would  be  greater  and  adduction  less;  for  instance,  at  15  ft.  abduction 
equals  about  10  to  12  degrees,  and  if  the  eyes  are  steadily  approached,  a  point  will 
finally  be  reached  where  abduction  and  adduction  are  equal. 


I04  FUNCTIONAL   ANOMALIES. 

anomalies.  Perhaps  this  confusion  hinges  on  the  neglect  of  many 
observers  to  distinguish  between  primary  adduction  (or  the  prism 
convergence  manifested  at  the  first  trial)  and  cramped  or  trained 
adduction  (the  prism  convergence  possible  v^hen  the  patient 
has  learned  to  temporarily  dissociate  accommodation  and 
convergence).  Moreover,  personal  equation  counts  for  no 
little  variation  in  the  results  of  different  investigators.  Stevens^ 
says:  "that  although  an  exact  standard  of  adduction  is  not 
to  be  expected,  should  the  adducting  ability  fail  to  reach 
50  degrees  (prism)  after  a  reasonable  amount  of  practice, 
it  is  likely  to  be  deficient."  Risley  ^  foundthe  average  adduction 
for  20  feet  in  25  non-asthenopic  individuals  to  be  25  degrees; 
while  Bannister,^  who  conducted  a  series  of  careful  studies  on 
100  soldiers  (all  in  fine  physical  condition),  found  the  average 
adduction  for  20  feet  to  be  14  degrees. 

It  seems  to  the  authors  that  Bannister's  statistics  indicate  plainly 
the  average  degree  of  primary  adduction,  while  Stevens  and 
Risley's  figures  have  reference  more  to  trained  adduction.  How- 
ever, it  must  be  borne  in  mind  that  convergence  and  divergence 
are  acts  so  intimately  bound  up  that  it  is  almost  impossible  to 
dissociate  them,  so  that  the  study  of  one  side  of  the  phenomenon 
necessarily  involves  the  other.  For  instance,  in  overcoming 
prisms  bases  in  (or  fusing  lights  through  prisms  held  bases  in 
before  the  eyes),  a  stimulus  to  divergence  is  created.  The  eye 
before  which  the  prism  is  placed  is  compelled  to  diverge,  in  order 
that  a  single  image  of  the  light  may  be  preserved.  It  will  be  no- 
ticed that  we  speak  here  of  divergence  and  not  of  the  external 
rectus,  because  all  muscles  which  help  to  turn  the  eye  out  are 
really  included  in  the  test.  When  the  prism  is  placed  before  one 
eye  only,  all  of  the  diverging  is  done  by  that  eye,  and  the  other 
unwaveringly  maintains  its  direction  toward  the  object  focused. 
Yet  it  does  not  follow  that  the  testing  is  confined  to  the  eye  that 
turns,  for  the  turning  eye  is  held  in  its  divergent  position  and  the 

'  Norris  &  Oliver,  "System  of  Diseases  of  the  Ej-e,"  Vol.  II,  1898. 
^  Univ.  Med.  Mag.,  January,  1895. 
^  Annals  of  Ophthal.,  January,  1898. 


HETEROPHORIA.  105 

Other  in  its  straight  position  by  a  contraction  of  all  the  external 
muscles,  and  therefore  we  are,  in  a  certain  sense,  testing  conver- 
gence and  divergence  at  the  same  time.  The  completed  action 
is  really  a  very  complicated  one.  For  example,  a  6  degree  prism 
is  held  base  in  before  the  right  eye;  in  order  to  overcome  the  momen- 
tary diplopia  induced  by  the  prism,  the  abductors  of  the  right  eye 
are  called  into  play  and  that  eye  diverged,  as  can  be  seen  through 
the  prism.  Strangely  enough,  the  left  eye  is  held  straight,  notwith- 
standing the  general  rule  that  movement  of  one  eye  in  any 
direction  is  always  accompanied  by  a  similar  associated  movement 
of  the  other  eye,^  and  that  therefore  the  adductors  of  the  left  eye 
tend  to  turn  that  eye  in  the  same  direction  as  its  fellow.  To 
neutralize  this  latter  impulse  the  abductors  of  the  left  eye  are 
called  upon  and  their  action  necessitates,  in  turn,  action  on  the 
part  of  the  adductors  of  the  right  eye,  which  would  immediately 
bring  the  right  eye  back  to  parallelism  were  not  the  abductors 
fully  occupied  in  keeping  it  in  such  position  as  to  avoid  diplopia. 
Hence  the  introduction  of  the  6  degree  prism  disturbed  the 
divergence  primarily  and  convergence  secondarily.  The  same 
phenomenon  occurs  when  prisms  are  placed  bases  out  before 
one  or  both  eyes.  In  testing  supra-  or  infraduction  a  similarly 
complicated  act  is  excited.  Thus:  when  a  2  degree  prism  is 
placed  base  down  before  the  right  eye,  the  image  falls  on  the  right 
retina  below  the  fovea,  in  consequence  of  which  the  elevators 
contract  and  the  right  eye  rolls  up,  turning  its  fovea  until  it 
reaches  the  position  of  the  displaced  image.  Naturally  an 
equal  stimulation  is  sent  to  the  elevators  of  the  left  eye  (accord- 
ing to  the  above-mentioned  rule  for  associated  eye-movements), 
but  a  change  in  the  position  of  the  left  fovea  would  destroy 
the  test  so  that  the  upward  impulse  of  the  left  eye  must  be  met 
by  an  equal  downward  impulse  of  the  right  eye,  which  is  pro- 
hibitive because  of  the  diplopia  that  would  be  sure  to  follow. 
Hence,  while  the  elevators  and  depressors  are  in  equilibrium, 
they  are  only  artificially  and  temporarily  so.     We  are  in  a  sense 

*  Movements  induced  by  prisms  not  too  strong  to  permit  fusion  constitute  the 
sole  apparent  exception  to  this  rule. 


io6 


FUNCTIONAL  ANOMALIES. 


determining  the  power  of  elevation  as  compared  with  that  of 
depression,  but  we  have  been  really  investigating  the  limits  of 
equilibrium  by  prism  stimulation  of  allied  and  of  antagonistic 
muscles. 

Further  knowledge  of  the  relations  of  convergence  and  diver- 
gence may  be  gained  from  the  use  of  Landolt's  ophthalmo- 
dynamometer (Fig.  47).     Just  as  in  the  study  of  the  accommoda- 


FiG.  47. — Landolt's  ophthalmo-dynamometer. 

tion,  we  learn  its  amplitude  by  estimating  the  position  of  the 
punctum  proximum  and  the  punctum  remotum,  so  in  the  study 
of  convergence  we  find  that  its  amplitude  is  equal  to  the  difference 
between  the  maximum  and  the  minimum  of  convergence.  Lan- 
dolt's device  consists  of  a  blackened  metallic  cylinder  which  is  to 
be  fitted  on  to  a  candle.  The  side  of  the  cylinder  turned  toward 
the  eye  presents  a  narrow  slit  (0.3  mm.),  which  is  illuminated 


HETEROPHORIA.  107 

by  the  flame  of  the  candle  and  serves  as  a  fixation  object.  Be- 
neath is  attached  one  end  of  a  spring  tape-measure,  graduated  on 
one  side  in  centimeters  and  on  the  other  in  the  corresponding 
numbers  of  meter-angles  (or  what  amounts  to  the  same  thing,  in 
diopters).  To  tind  the  punctum  proximum  of  convergence,  the 
case  holding  the  tape-measure  is  held  beside  one  of  the  eyes  and 
the  cylinder  drawn  about  two-thirds  of  a  meter  away  from  it, 
directly  in  front  of  both  eyes,  with  the  illuminated  slit  turned  to- 
ward the  patient,  who  then  fixes  on  the  light  streak  while  it  is 
moved  directly  in  the  median  line  closer  and  closer  to  the  eyes.  The 
moment  the  streak  of  Hght  begins  to  broaden  or  double,  the  point 
of  greatest  possible  accurate  convergence  has  been  reached,  when 
one  side  of  the  tape  will  indicate  in  centimeters  the  distance  of  the 
punctum  proximum  of  convergence,  and  the  other  side  the  corres- 
ponding maximum  of  convergence  in  meter-angles;  for  instance, 
a  convergence  nearpoint  of  ii  c.c.  corresponds  to  9  meter-angles. 
In  the  mentally  dull,  the  examination  can  be  made  much  easier 
by  having  a  colored  glass  before  one  eye  so  that  doubling  of  the 
light  streak  will  be  recognized  the  instant  it  occurs.  A  much 
simpler  method  that  we  have  used  for  6  to  8  years  past,  is  to 
employ  the  small  electric  Hght  used  in  making  the  Maddox 
rod  test  at  the  reading  distance.  If  in  a  darkened  room  this 
small  light  is  held  13  inches  from  the  eyes  of  the  patient  a  tiny 
bright  image  of  it  is  seen  in  the  center  of  each  cornea.  As  the 
light  is  carried  toward  the  eyes  and  they  follow  it  in,  the 
images  also  move  inward  toward  the  nose;  but  when  the  light  has 
been  approximated  to  within  about  4  inches  of  the  root  of  the 
nose,  one  or  both  eyes  of  the  average  patient  will  refuse  to  further 
converge  and  the  bright  corneal  image  will  be  seen  to  roll  out- 
ward. The  moment  the  break  occurs  marks  the  near  point  of 
convergence.  For  instance,  if  one  eye  breaks  away  from  the  con- 
vergence act  at  5  inches  this  is  the  convergence  near  point 
(C.  N.  P.)  and  expressed  in  meter  angles  would  equal  8  meter 
angles.  A  3-inch  convergence  near  point  would  equal  13  meter 
angles  (M.  A.),  and  a  2-inch  convergence  near  point  would  equal 
20  meter  angles  of  convergence. 


Io8  FUNCTIONAL  ANOMALIES. 

The  minimum  of  convergence  (or  convergence  far  point)  is 
determined  by  the  following  method:  Make  the  patient  fix  the 
flame  of  a  candle  at  a  distance  of  6  meters  or  more  and  find  the 
strongest  prism  base  in  before  one  eye  that  can  be  overcome 
without  causing  homonymous  diplopia,  then  divide  the  number 
of  the  resultant  prism  by  7,  to  obtain  approximately  in  meter- 
angles  the  amount  of  deviation  of  each  eye.  Thus,  if  abduction 
at  20  feet  is  7  degrees  the  minimum  of  convergence  is  i.oo 
meter-angle;  if  8  degrees  it  is  1.14  meter-angles;  and  if  6 degrees, 
it  is  0.85  meter-angle. 

In  the  normal  state  the  average  maximum  of  convergence  (p) 
is  about  10.5  meter-angles  (about  31/2  inches  as  the  conver- 
gence near  point)  and  the  average  minimum  of  convergence  (r), 
about  I  meter-angle;  therefore  the  mean  amplitude  of  conver- 
gence (a),  as  expressed  by  Landolt^  would  be,  a=io.5  — (  — 1)  = 
II. 5  m.  a.,  or  if  the  maximum  be  12.5  meter-angles  and  the 
minimum  1.5  meter-angles  the  amplitude  of  convergence  would  be 
14  meter-angles.  The  calculation  is  one  of  simple  addition  and 
subtraction,  and  it  will  be  observed  that  it  takes  account  not  only 
of  convergence,  but  that  it  also  reckons  the  extreme  limit  of  diver- 
gence (as  found  with  prisms)  as  the  measure  of  the  minimum  of 
convergence,  a  fact  that  the  student  will  do  well  to  ponder  and 
settle  for  himself  before  proceeding  to  the  study  of  any  practical 
office-problems  in  anomalies  of  convergence  and  divergence. 
As  above  stated,  the  two  acts  are  so  intimately  bound  up  that  it  is 
relatively  impossible  to  dissociate  them,  and  investigation  of  one 
side  of  the  question  necessarily  involves  the  other. 

Careful  weighing  of  all  the  facts  connected  with  musculodyna- 
mics  seems  to  warrant  the  following  tentative  conclusions: 

1.  That  the  degree  of  adduction  (prism  convergence)  for  6 
meters  given  by  most  writers  as  proper  in  the  first  office-examina- 
tion cannot  be  reached  by  healthy  eyes  except  after  practice  in 
prism  convergence. 

2.  That  primary  adduction  at  the  first  office-examination 
will  often  not  exceed  20  degrees. 

'  The  Refraction  and  Accommodation  of  the  Eye,  iS86. 


HETEROPHORIA.  109 

3.  That  adduction  (prism  convergence)  can  often  be  quickly 
trained  to  50  degrees  and  not  infrequently  to  75  degrees,  and  in 
some  cases  even  to  90  or  100  degrees. 

4.  That  estimation  of  the  amplitude  of  convergence  is  the  best 
test  of  the  real  power  of  convergence  and  its  limits. 

5.  That  abduction  as  found  at  the  first  office-examination  is 
fairly  constant,  and  in  orthophoria  will  rarely  fall  below  7  degrees. 

That  the  ratio  between  adducton  (prism  convergence)  and 
abduction  (prism  divergence)  for  20  ft.,  ranges  from  8  to  2  1/2:1 
No  arbitrary  standard  can  be  fixed  as  yet,  simply  because  the 
figures  thus  far  off'ered  have  been  largely  a  matter  of  personal 
equation. 

MEASUREMENT  OF  ARC  ROTATIONS. 

It  is  well  to  supplement  prism  rotations  by  the  estimate  of 
the  arc  rotations  in  all  hyperphorias  of  any  degree  and  in  all 
lateral  deviations  of  an  obscure  nature.  The  hand  perimeter 
of  Schweigger  is  well  adapted  to  this  purpose  and  is  used  as 
follows :  The  perimeter  is  held  by  the  patient  in  the  same  position 
as  for  ordinary  perimetry.  A  black  strip  on  which  a  2  or  3  letter 
word  in  ordinary  print  is  pasted  is  then  started  from  the  fix- 
ation point  and  moved  as  far  up,  down,  in  and  out  as  the 
patient  can  carry  the  eye  and  still  read  the  word  without  moving 
the  head.  These  figures  are  noted  and  entered  on  an  ordinary 
perimetric  chart  and  when  the  points  thus  charted  are  connected 
by  lines  a  fair  idea  may  be  gotten  of  the  arc  rotations  of  the  eye. 

This  method  is  really  of  value  in  many  cases,  but  fails  of 
necessity  in  presbyopes  who  would  have  to  wear  glasses  during 
the  test.  The  moment  the  test  object  or  word  passes  beyond  the 
degree  marking  the  edge  of  the  glass  the  test  loses  all  value.  The 
instrument  applicable  in  all  cases  is  that  devised  by  Stevens  known 
as  the  tropometer  (Fig.  48).  "  It  consists  essentially  of  a  telescope, 
in  which  an  aerial  image  of  the  cornea  is  formed  near  the  eye- 
piece. A  scale,  graduated  to  measure  the  rotations  of  the  eye  in 
all  directions,  is  placed  at  the  point  where  the  image  is  formed." 
After  placing  the  head  in  the  head-rest,  so  that  the  glabella  and 


no 


FUNCTIONAL  ANOMALIES. 


the  commiss  ure  of  the  upper  Hp  are  exactly  vertical,  the  patient 
fixes  on  the  center  of  the  object-glass.  Under  the  direction  of  the 
surgeon,  the  patient  turns  the  eye  under  examination  to  the  full- 
est extent  in  the  four  principal  meridians,  while  the  head  is  kept 
absolutely  immovable.     The  effect  registered  on  the  scale  by 


Fig.  48  —The  tropometer  (Annales  d' Oculisiique,  English  edition,  July,  1895). 


movement  of  the  cornea  is  shown  in  Fig.  49.     These  rotations 
are  given  approximately  as  follows: 

Upward 33  degrees  (of  arc). 

Downward 50  degrees  (of  arc). 

Inward 48  to  53  degrees  (of  arc). 

Outward 48  to  53  degrees  (of  arc). 

Our  own  figures  for  100  eyes  with  normal  muscular  balance 
show  the  following  average  rotations  with  the  tropometer: 

Nasal  52  Temporal  50 

Upward  32  Downward  56 


HETEROPHORIA. 


Ill 


They  represent  the  four  principal  arc  rotations.  In  all  the 
degrees  of  the  circle  between  them,  the  rotations  will  be  accom- 
plished by  the  combined  action  of  the  muscles  normally  turning 
the  cornea  to  these  positions,  and  when  these  points  have  been 
found  and  connected  they  map  out  the  monocular  field  of  fixation. 
This  varies  much  however,  according  to  different  observers. 
The  discrepancies  arise  from  variations  in  the  normal  power  of 
the  muscles  of  one  individual  as  compared  with  another,  and 
the  amount  of  attention  and  effort  of  which  an  individual  is 
capable. 


60- 
*0  — 


A. 


XP" 


f> 


-■to 

-60 


Fig.  49. — Scale  for  tropometer. 

The  field  of  binocular  fixation  comprises  that  part  of  the  visual 
or  form  fields  that  is  visible  to  both  eyes  at  the  same  time  without 
movement  of  the  head,  but  with  movement  of  the  eyes.  It  is 
not  necessarily  identical  with  the  field  of  binocular  single  vision, 
although  the  limits  are  practically  the  same.  Near  the  periphery 
of  the  field  of  binocular  fixation,  the  images  of  the  object  may 
not  fall  upon  the  yellow  spot  of  each  eye,  but  upon  adjoining 
portions  of  the  retina,  when  insuperable  diplopia  will  be  mani- 
fest.    The  field  of  binocular  vision  is  smaller  than  the  united 


112 


FUNCTIONAL   ANOMALIES. 


fields  of  each  eye,  and  that  of  binocular  single  vision  is  still 
smaller.  The  limits  of  both  may  be  readily  determined  by  peri- 
metric measurement,  using  one  or  two  small  white  dots  on  a 
black  background  or  black  dots  on  a  white  background.  Those 
dots  on  the  periphery  where  the  single  dot  doubles  or  blurs, 
represent  the  limits  of  the  field  of  single  vision.  They  are 
approximately : 

Up 60  degrees  (Pooley) 45  degrees  (Duane). 

Down. .    70  degrees  (Pooley) 70  degrees  (Duane). 

Right  and  left  60  degrees  (Pooley).  .55  degrees  (Duane). 

In  old  age  the  rotations  are  lessened,  and  in  determining  them 
at  any  age,  the  form  and  position  of  the  globe  in  the  orbit  and 


Fig.  50. 

the  orbital  bones  must  be  taken  into  consideration.     Such  wide 
variations  as  are  shown  in  the  averages  given  above  are  confusing 


HETEROPHORIA.  II3 

to  one  who  endeavors  to  determine  whether  a  certain  movement 
is  normal  or  otherwise.  An  excess  of  t,t,  degrees  upward  or  of 
55  degrees  downward  rotation  should  direct  suspicion  to  the 
vertical  muscles,  and  if,  in  the  presence  of  esophoria  or  exophoria, 
the  temporal  and  nasal  rotations  are  normal,  operation  on  the 
lateral  muscles  will  scarcely  be  recommended  and  is  justifiable 
only  when  the  vertical  muscles  have  been  exonerated  of  causative 
influence  by  careful  estimation  of  their  rotations;  this  is  especially 
important  because  high-grade  lateral  deviation  tendencies  are 
often  an  indication  of  unequal  vertical  tensions.  It  may  be  well 
to  note,  in  passing,  that  the  surgeon  may  learn  by  means  of  the 
tropometer  the  peculiarity  of  his  own  muscular  status  with  re- 
spect to  the  horizon  before  proceeding  to  the  use  of  the  clinoscope 
(Fig.  50),  also  devised  by  Stevens,  for  accurate  study  of  the 
horopter  in  all  cases  of  anaphoria  or  anatropia,  also  cataphoria 
or  catatropia.^  In  case  the  observer  is  exophoric  or  esophoric, 
the  tubes  may  be  adjusted  in  divergence  or  convergence,  and  in 
case  of  hyperphoria  a  correcting  prism  may  be  placed  in  a  clip 
next  the  eye.- 

'  Anaphoria.  Latent  deviation  of  both  visual  axes  above  the  horizontal  plane  of 
the  head. 

Cataphoria.  Latent  deviation  of  both  visual  axes  below  the  horizontal  plane  of 
the  head. 

Anatropia.  Manifest  (apparent)  deviation  of  both  visual  axes  above  the  hori- 
zontal plane  of  the  head. 

Catatropia.  Manifest  (apparent)  deviation  of  both  visual  axes  below  the  hori- 
zontal plane  of  the  head. 

^  Monocular  diplopia  is  the  result  of  irregular  corneal  or  lenticular  curvature,  or  of 
disease  of  the  foveal  region,  and  bears  no  relation  to  the  subject  under  discussion. 


ESOPHORIA. 


Symptoms. — The  symptoms  of  the  tendency  of  the  visual 
axes  toward  each  other  are  local  or  ocular,  and  general  or  retlex. 
They  vary  according  to  the  degree  of  the  esophoria  and  the  sus- 
ceptibility of  the  patient.  The  local  symptoms  are  in  no  wise 
distinctive.  They  are :  Pain  in  the  eyes  and  in  their  immediate 
neighborhood,  flushing  of  the  conjunctiva  after  use,  photophobia, 
lacrimation,  blurring  of  the  print  in  reading,  and  inability  to 
continue  for  any  length  of  time  the  effort  of  looking  at  near  or 
distant  objects  without  becoming  drowsy.  As  will  be  seen,  the 
same  symptoms  may  depend  upon  hyperopia  or  astigmatism, 
or  any  other  muscular  or  refractive  error.  The  reflex  symptoms 
are  exceedingly  complex  and  unstable,  and  they  vary  from  an 
occasional  slight  headache  to  intense  migraine;  from  a  simple 
restlessness  to  serious  functional  nerve-diseases,  from  a  chronic 
insignificant  disturbance  of  digestion  to  loss  of  appetite,  inter- 
rupted digestion,  and  vomiting.  A  peculiarity  of  esophoria, 
not  found  among  symptoms  of  refractive  or  other  muscular 
anomalies,  is  that  the  patient  often  complains  of  seeing  his  nose, 
especially  in  close  work.  This  symptom  is  largely  imaginary, 
for  the  patient  is  no  more  inclined  by  esophoria  to  turn  his  eye 
in  so  far  that  coordination  will  be  lost,  than  he  is  to  have  double 
vision  for  all  objects.  The  complaints  are  not  limited  to  the 
time  of  using  the  eyes,  but  often  follow  for  many  hours  after  a 
continued  or  unusual  strain.  Identical  symptoms,  although 
perhaps  not  so  severe,  arise  from  gazing  intently  in  the  eft'ort  to 
see  clearly  a  distant  object.  Esophorics  invariably  are  disturbed 
by  traveling  in  the  train,  by  looking  at  rapidly  moving  objects, 
by  shopping,  and  after  the  theatre  or  opera.  The  symptoms  are 
due,  not  directly  to  the  internal  muscles,  but  to  the  constant 

114 


ESOPHORIA.  115 

effort  under  which  the  patient  labors  to  prevent  abnormal  con- 
vergence. A  tendency  inward  can  be  controlled  only  by  an  equiv- 
alent tension  on  the  muscles  of  divergence.  If  the  defect  is  so 
high  that  the  external  muscles  cannot  constantly  maintain  coordi- 
nation of  the  visual  axes,  and  one  eye  turns  inward,  the  symp- 
toms may  be  immediately  relieved,  but  the  patient  will  complain  of 
diplopia.  It  is  not  always  the  highest  degree  of  defect  that  gives 
rise  to  the  severest  symptoms.  The  disturbances  above  described 
never  arise,  for  instance,  in  cases  of  manifest  internal  squint. 
It  can  be  readily  understood  that  the  constant  strain  on  the  ab- 
ductors to  maintain  parallelism  of  the  visual  axes  may  give  rise, 
in  certain  subjects,  to  alarming  reflex  neuroses.  No  set  of 
muscles,  in  any  part  of  the  body,  can  be  in  a  state  of  constant 
contraction  without  making  a  deep  impression  on  the  nervous 
system.  Indeed,  hypnotic  states  are  induced  through  an  analogous 
process.  The  severity,  then,  of  the  symptoms  must  depend 
almost  entirely  upon  the  susceptibility  of  the  individual  to  abnor- 
mal impressions,  and  the  patients  who  suffer  most  in  esophoria 
are  those  who  habitually  complain  severely  from  apparently 
insignificant  causes. 

Etiology. — The  causes  that  contribute  to  the  abnormal  ten- 
dency of  the  visual  axes  inward  are  local  and  constitutional.  In 
many  cases,  it  is  quite  impossible  to  satisfactorily  explain  the 
origin  or  the  existence  of  esophoria.  It  may  be  stated,  however, 
in  general  terms  that  it  is  found  most  frequently  in  persons  of  a 
neurotic  disposition  who  have  low  grades  of  H.  Ah  or  H.  The 
susceptibility  of  the  nervous  system  plays  a  most  important  role 
in  the  causation  of  muscular  anomalies,  particularly  esophoria. 
By  that  expression  is  meant  an  abnormally  acute  impressionabil- 
ity of  the  nervous  system  induced  by  lack  of  proper  nourish- 
ment from  deficiency  of  oxygenated  blood,  a  stasis  of  the  venous 
or  arterial  supply  from  disturbance  of  the  circulatory  system — 
in  short,  a  neurotic  disposition.  That  an  underlying  predisposi- 
tion to  irregular  nerve-activity  is  an  essential  contributing  factor 
in  the  development  of  the  muscular  imbalance  and  the  symptoms 
accruing  from  it  is  demonstrated  by  the  well-known  fact  that  many 


Il6  FUNCTIONAL   ANOMALIES. 

individuals,  who  have  the  theoretic  local  conditions  assumed  to 
give  rise  to  muscular  asthenopia,  use  their  eyes  constantly 
without  discomfort;  furthermore,  in  the  absence  of  the  local 
causes  that  are  conceded  to  produce  esophoria,  and  in  the  pres- 
ence of  those  that  are  usually  causative  of  exophoria,  esophoria 
is  often  present  and  gives  rise  to  no  symptoms.  Identical  in- 
consistencies are  illustrated  in  the  study  of  the  etiology  of  other 
than  eye  diseases.  Two  persons  exposed  to  the  same  influences 
will  be  seized  with  different  affections  or  one  will  entirely  escape. 
It  is  not  strange,  therefore,  that  we  are  often  at  a  loss  to  ascribe 
the  mysterious  unbalancing  of  the  ocular  muscles  to  a  competent 
cause,  and  are  compelled  to  invoke  the  aid  of  the  supposition  of  a 
deranged  nervous  organization. 

The  interdependent,  constant,  tenacious  relation  between  the 
intra-  and  extra-ocular  muscles  furnishes  an  explanation  of  the 
existence  of  esophoria  in  a  majority  of  cases.  In  health  there  is  a 
certain  related  range  of  accommodation  and  convergence;  every 
contraction  of  the  ciliary  muscle  is  accompanied  by  contraction 
of  the  adductors,  or  stimulus  to  the  accommodation  means 
stimulus  to  convergence.  In  emmetropia  the  meter-angle  of 
convergence  is  determined  by  the  diopters  of  accommodation. 
Thus,  accommodation  of  3  diopters  induces  convergence  of  3 
meter-angles.  Now  if,  for  any  reason,  an  abnormal  amount  of 
accommodation  is  required  to  read  at  the  ordinary  near  point 
(thus  overstepping  the  normal  range)  a  correspondingly  increased 
demand  on  convergence  is  made,  and  a  tendency  to  converge  the 
visual  axes  to  a  point  within  the  desired  reading  distance  results. 
When,  notwithstanding  this  unbalanced  relation,  the  normal  con- 
vergence of  the  visual  axes  is  maintained,  it  can  only  be  at  the 
expense  of  the  relative  accommodation  and  convergence,  and  in 
any  case  it  entails  an  unusual  resistance  on  the  part  of  divergence. 
If  the  range  of  the  relative  accommodation  and  convergence  is 
not  exceeded  in  this  effort  to  secure  binocular  fixation  at  the  read- 
ing distance,  there  will  be  no  esophoria  and  no  symptoms,  and  this 
probably  explains  the  exemption  of  certain  individuals.  The 
refractive  conditions  that  most  frequently  give  rise  to  a  disruption 


ESOPHORIA.  117 

of  the  relative  range  are  hyperopia,  hyperopia  astigmatism 
(simple  and  compound)  and  low  myopic  astigmatism.  To  over- 
come hyperopia  states  of  the  refraction  and  thus  secure  good 
acuity  of  vision  for  both  distance  and  near,  unusual  demand  is 
made  on  the  ciliary  muscles,  which  in  turn  stimulates  all  the  other 
muscles  supplied  by  the  3rd  nerve.  Hence,  an  inward  tendency 
of  the  visual  axes  is  originated,  but  this,  in  the  interest  of  binocular 
single  vision,  is  suppressed  and  the  condition  remains  a  tendency 
only.  The  same  reasoning  applies  to  hyperopia  astigmatism; 
myopia  astigmatism  of  low  grade  is  also  a  frequent  and  potent 
cause  of  ciliar\^  spasm,  and  thus  may  be  classed  among  the  causes 
of  esophoria. 

Treatment. — WTien,  by  means  of  one  or  all  the  tests  described 
on  page  88,  inward  tendency  of  the  visual  axes  has  been  repeatedly 
and  conclusively  determined,  we  are  confronted  with  the  practical 
problem  of  relief.  The  method  selected  depends  upon  i,  the 
severity  of  the  symptoms,  and  2,  the  degree  of  the  esophoria. 
We  recommend  the  adoption  of  the  following  course: 

First.  Use  of  a  Proper  Correction. — In  all  cases  the  estimation 
of  any  optical  defeat  under  complete  paralysis  of  accommodation 
and  the  wearing,  for  some  weeks,  of  as  nearly  a  full  correction 
as  can  he  home  with  comfort.  This  is  essential.  No  other  treat- 
ment directed  to  the  restoration  of  the  lost  equilibrium  of  the 
muscles  should  be  inaugurated  until  glasses  correcting  the  ame- 
tropia have  been  worn  sufficiently  long  to  remove  any  pernicious 
influence  born  of  constantly  over-taxed  accommodation.  The 
experience  of  all  ophthalmologists  confirms  this  statement,  and  no 
surgeon  of  judgment  or  ability  will  apply  treatment  directly 
to  the  muscles  until  he  has  given  the  patient  the  opportunity  to 
be  cured  by  wearing  glasses.  Any  co-existing  general  distur- 
bance must  also  be  relieved  by  appropriate  medication.  Diet 
should  be  regulated,  exercise  in  the  open  air  instituted,  the  time 
devoted  to  reading  restricted;  in  short,  every  means  tending  to 
diminution  of  the  unwonted  excitability  of  the  nervous  system, 
or  the  derangement  of  any  of  the  vital  functions,  must  be  employed. 

Second.     Convergence   and   Accommodation  Repression. — Inas- 


ir8  FUNCTIONAL   ANOMALIES. 

much  as  excessive  accommodative  effort  is  a  chief  agent  in  the 
production  of  annoying  esophoria,  it  is  well  to  try  to  remedy  the 
abnormal  convergence  effort  by  quieting  the  overactive  accom- 
modation if  possible.  Should  the  use  of  a  proper  correcting 
glass  prove  insufhcient  to  allay  the  patient's  symptoms,  resort 
may  be  had  to  the  use  of  a  plus  2  or  3  diopter  spherical  lens  to  be 
used  in  addition  to  the  regular  correction  by  means  of  a  hook 
front  or  other  device.  With  this  the  patient  w^ill  read  or  sew  for 
15  minutes  to  half-an-hour,  two,  three  or  four  times  a  day  for  two 
to  four  weeks.  Complaint  will  of  course  be  made  that  the  read- 
ing or  sewing  must  be  brought  very  close  to  the  eyes,  but  if  the 
patient  is  reassured  he  will  generally  persist.  Some  drift  readily 
into  the  practice,  some  with  difficulty  and  much  persuasion,  and 
some  never.  It  will  seldom  be  necessary  to  resort  to  it  save  in 
esophoria  of  6  degrees  or  more.  In  some  cases  the  results  are 
peculiarly  gratifying  and  in  others  are  a  total  failure. 

Third.  Prism  Exercise  and  Nerve  Sedatives. — By  means  of 
frequent  and  interrupted  use  of  prisms,  we  endeavor  to  strengthen 
the  power  and  increase  the  range  of  divergence,  and  unless 
there  is  actual  preponderance  of  convergence,  some  cases  of 
recent  standing  may  be  effectually  treated  by  this  method. 
Abduction  normally  equals  7  or  8  degrees  w^hen  tested  with  a 
candle  at  20  feet.  In  esophoria,  abduction  sometimes  falls  to 
I,  2,  or  3  degrees,  and  the  normal  ratio  between  abduction  and 
adduction  (about  i  to  3  or  4)  is  lost.  A  prism  of  6  degrees,  axis 
horizontal,  is  placed  base  in  before  the  patient's  eye,  and  the 
patient  is  instructed  to  look  at  the  candle-flame  20  feet  distant. 
If  his  abduction  equals  3  degrees,  the  prism  will  produce  insuper- 
able homonymous  diplopia;  but  if  he  advance  to  within  a  few  feet 
of  the  candle  flame,  abduction  increases  as  he  advances,  and  he 
will  reach  a  point  where  the  two  lights  will  fuse.  He  now  re- 
cedes from  the  candle,  maintaining  its  image  single  as  long  as 
possible.  When  the  images  have  again  separated  he  approaches 
the  candle  until  the  lights  are  fused,  when  he  again  recedes.  This 
may  be  repeated  a  number  of  times,  but  no  longer  than  five 
minutes  at  one  sitting.     On  the  second  trial  he  will  find  that  the 


ESOPHORIA. 


119 


C 


lights  fuse  easier  than  at  the  first.  At  the  third  trial  it  will  be 
still  easier,  and  in  the  course  of  a  few  days  he  will  be  able  to  fuse 
the  lights  at  20  feet.  This  exercise  should  be  continued  until 
asthenopic  symptoms  have  disappeared  for  some  weeks.  The 
prism  may  be  placed  before  either  eye,  or  before  one  and  then  the 
other,  and  the  effect  will  be  the  same.  Fusion  of  the  lights  is  not 
the  result  of  contraction  of  one  or  the  other  externus  alone,  but 
is  accomplished  by  forced  action  of  all  the  muscles  which  partic- 
ipate in  divergence — an  extremely  complicated  function.  (See 
Weiland's  article  in  Arch,  of  OphthaL,  January,  1898.)  In  our 
experience,  however,  prism  exercise  has  quite  as  often  aggravated 
the  symptoms  as  it  has  relieved  them.  ^ 

A  useful  adjunct  to  the  prism  exer- 
cise is  the  internal  administration  of 
the  tincture  of  belladonna,  hyoscya- 
mus,  bromides,  or  some  of  the  other 
sedatives,  in  as  large  doses  as  can  be 
well  borne.  The  effect  of  these 
remedies  is  to  diminish  the  spasm 
or  abnormal  contraction  of  the  ad- 
ductors and  benumb  the  sensitive- 
ness of  the  nervous  system. 

Fourth.  Correction  by  Prisms  in 
the  Position  of  Rest. — When,  after 
appropriate  trial  by  means  of  the 
above  remedies  and  methods,  it  is 
felt  that  something  must  be  done, 
and  operation  is  out  of  the  ques- 
tion, the  symptoms  may  sometimes  be  relieved  by  the  use  of 
prisms,  bases  out,  which  correct  a  portion  of  the  esophoria 
(Fig.  51).  The  degree  of  the  defect  requiring  the  use  of  prisms 
varies  from  6  to  15  degrees.  Defects  under  6  degrees  may  fre- 
quently be  corrected  without  them,  while  those  higher  than  10 
degrees  sometimes  necessitate  operation.  The  degree  of  the  de- 
fect is  determined  in  every  instance  by  the  result  of  testing  at  20 
feet.     A  constant  relation  does  not  exist  between  the  convergence 


Fig.  51. — Effect  of  diverging  prisms 
on  excessive  convergence. 


I20  FUNCTIONAL   ANOMALIES. 

for  distance  and  for  the  near  point  in  cases  where  equilibrium  has 
been  lost.  For  instance,  a  defect  of  7  or  8  degrees  for  distance 
may  be  the  same,  or  less,  or  more,  at  the  near  point,  depending 
upon  various  concomitant  conditions.  The  strength  of  prism 
should  be  much  less  than  the  total  amount  of  defect.  It  is  well 
for  the  novice  to  feel  his  way  and  not  order  more  than  i  degree  of 
prism  base  out  in  each  eye  as  an  experiment.  It  is  a  question 
whether  wearing  a  prism  correction  does  not  develop  an  increase 
in  the  error;  the  very  principle  of  its  action  forbids  a  cure.  Under 
such  treatment  the  tendency  of  esophoria  is  to  increase,  but  whether 
this  increase  is  due  directly  to  the  effect  of  wearing  the  prisms  or  to 
the  unmasking  of  a  latent  defect  is  uncertain.  Should  the  general 
health  be  improved  by  medication,  change  of  environment,  or  oc- 
cupation, etc.,  the  defect  may  become  less,  but  not  often  can  this 
improvement  be  ascribed  to  the  prisms.  It  is  oftener  the  case  that 
stronger  and  stronger  prisms  will  be  required  to  relieve  the  symp- 
toms, and  occasionally  the  case  comes  to  operation.  Our  plan  is  to 
allow  the  patient  to  wear  his  prism  correction  without  change  as 
long  as  he  is  comfortable,  permitting  him  to  decide  whether  it  shall 
be  worn  constantly  or  only  for  near  work.  In  most  instances, 
constant  wearing  only  will  give  relief.  It  must  be  remembered 
that  esophoric  patients  do  not  complain  of  headache  or  other 
symptoms  consequent  upon  prolonged  use  of  the  eyes  at  the  near 
point  only,  but  intense  gazing  at  objects  in  the  distance,  such  as 
the  preacher  in  his  pulpit,  looking  steadily  from  a  car  window,  or 
gazing  at  objects  that  are  themselves  moving,  will  give  rise  to  these 
symptoms.  The  directions  to  the  patients  should  be  modified 
according  to  their  occupation  and  symptoms,  allowing  them  to 
judge  as  to  the  occasions  when  it  will  be  necessary  to  wear  the 
glasses.     The  following  case  is  in  point : 

F.  E.,  aged  ten,  is  referred  by  his  family's  general  medical 
adviser,  who  has  exhausted  his  resources  in  endeavoring  to  quiet 
the  boy's  blepharospasm  and  general  nervous  irritability.  Cir- 
cumcision had  been  done  and  adenoids  removed  in  hope  of 
benefiting  him,  but  without  avail.  The  child  was  undersized 
for  his  age  and  the  son  of  a  neuropathic  father  and  a  gela- 


ESOPHORLV.  121 

tinous  mother.  His  vision  equalled  5/5  in  each  eye;  his  accom- 
modation was  normal.  Esophoria  of  10  degrees  was  present 
and  no  hyperphoria.  Under  atropin  refraction  was  found  to  be 
+  2.00  sph.  in  each  eye.  Because  of  his  esophoria  +  1.75  sph. 
was  ordered  for  constant  wear,  but  the  child  absolutely  refused  to 
wear  the  glasses  because  of  blurred  distant  vision;  +1.25  sph. 
was  therefore  ordered  arid  worn  with  some  relief  to  the  symptoms, 
but  six  months  later  at  the  end  of  the  school  year  the  blepharo- 
spasm was  as  bad  as  ever.  Convergence  and  accommodation 
repression  were  then  tried,  but  as  the  family  offered  no  cooperation 
it  was  finally  decided  to  combine  a  i  degree  prism  base  out  in 
each  glass  with  the  +1.25  sph.  In  four  weeks  the  blepharospasm 
had  entirely  disappeared  and  in  four  years  has  not  reappeared. 
Today,  after  four  years,  he  wears  a  2  degree  prism  base  out  with 
+  1.50  sph.  in  each  eye.  His  total  esophoria  is  12  degrees,  an  in- 
crease of  but  2  degrees  in  four  years  and  the  boy  is  growing  finely 
and  does  his  school  work  without  any  complaint  whatever.  It  is 
quite  possible  that  after  he  passes  through  puberty,  the  prisms 
may  be  taken  out  of  his  glasses  and  accommodation  repression  be 
invoked  to  allay  any  symptoms  he  may  develop.  Prisms  in  the 
position  of  rest  give  relief  because,  while  worn,  the  patient's 
eyes  are  allowed  to  assume  a  position  W'hich  is  one  of  rest  for 
them,  and  objects  are  held  single  by  the  refracting  power  of  the 
prisms.  In  esophoria  the  visual  axes  have  become  converged,  and 
prisms,  bases  out,  bend  the  rays  proceeding  from  the  object 
outward  toward  the  new  position  occupied  by  the  fovea  centrales. 
Here  the  position  of  rest  is  not  parallelism,  but  convergence. 
The  tendency  to  turn  has  become  an  appreciable  turning.  Prisms 
must  be  regarded  as  crutches  that  will  permit  the  patient  to 
travel  comfortably  over  his  rough  road,  rather  than  as  a  means  of 
final  cure. 

Fifth.  Operation. — ^In  all  cases  operation  should  be  reserved 
as  the  last  resort.  In  low  grades  of  esophoria — in  fact,  in  all 
grades  of  esophoria  not  bordering  on  esotropia,  the  means  recom- 
mended under  paragraphs  i,  2,  3,  and  4  should  be  given  a  proper 
trial  and  cannot  be  too  much  emphasized.     Some  writers  go 


122  FUNCTIONAL   ANOMALIES. 

even  farther  than  this  and  state  that  no  benefit  whatever  is  derived 
from  operation.  Our  experience  does  not  justify  this  statement. 
We  are  convinced  that  many  cases  are  operated  upon  that  could 
be  relieved  by  less  radical  measures,  and,  on  the  other  hand, 
we  have  operated  where  other  means  have  been  tried  and  failed 
and  have  been  entirely  successful.  The  measure  of  success  is 
the  cessation  of  the  symptoms  and  the  restoration  to  equilibrium 
of  the  muscles.  The  condition  known  as  equilibrium  varies,  as 
has  been  before  noted,  from  esophoria  of  2  degrees  for  20  feet,  to 
exophoria  of  2  degrees  for  the  reading  distance.  But  it  is  our 
opinion  that  equilibrium  or  orthophoria  is  present  only  when, 
by  testing  with  the  Maddox  rod,  the  streak  of  light  passes  directly 
through  the  center  of  the  flame  horizontally  and  vertically. 
Having  decided  that  surgical  procedure  is  necessary,  we  have  the 
choice  of  advancement  of  the  external  recti  or  tenotomy  of  the 
interni.  According  to  Landolt,  tenotomy  is  never  in  place — 
advancement  is  the  only  surgical  means.  He  bases  this  opinion 
upon  the  assumption  that,  in  all  cases,  "the  defect  arises  from  a 
loss  of  divergence  and  not  an  increase  or  spasm  of  convergence; 
hence  a  weakening  of  the  muscles  which  are  not  too  strong  is 
wrong  in  principle."  If  esophoria  depends  on  hyperopia  or  hyper- 
opic  astigmatism — in  other  words,  if  the  abnormal  convergence  is  a 
reflex  from  unusual  activity  of  the  accommodation,  the  tendency  of 
the  visual  axes  inward  is  not  a  result  of  an  insufficiency  of  diver- 
gence, but  a  physiologic  sequence  to  inordinate  action  of  the 
ciliary  muscle,  producing  excessive  convergence.  Hence,  in 
esophoria,  tenotomy  of  the  interni  is  more  often  productive  of  good 
results  than  advancement  of  the  externi.  Moreover,  adjustment 
of  the  ocular  axes  is  much  more  precise  with  tenotomy  than  with 
advancement.  All  such  operations  should  be  done  under  local 
anesthesia,  so  that  the  patient  maybe  brought  to  the  sitting  posture 
and  the  final  result  controlled  by  some  one  of  the  tests  alluded  to. 
It  is  not  practicable  to  state  in  precise  terms  the  exact  degree  of 
esophoria  that  demands  or  justifies  tenotomy  or  to  make  an  arbi- 
trary law,  any  more  than  it  is  reasonable  to  say  that  in  hyper- 
metropia  a  certain  number  of  diopters  or  fractions  of  a  diopter 


ESOPHORLV.  123 

must  be  deducted  from  the  full  correction.  The  decision  as  to 
operation  depends  upon  the  effect  of  the  methods  of  treatment 
previously  outlined  and  on  the  severity  of  the  symptoms.  If  we 
find  that  under  accommodation  repression,  prism  exercise  and 
internal  medication  the  defect  remains  unchanged  or  slightly 
improves,  and  the  symptoms  become  less  and  less  annoying,  even 
though  the  degree  of  esophoria  be  moderately  high,  operation  is 
not  to  be  recommended.  And,  on  the  other  hand,  if  a  moderately 
low  degree  is  associated  with  severe  symptoms  and  only  partial 
relief  results  from  the  wearing  of  prisms,  operation  is  to  be  con- 
sidered. In  our  own  practice  we  are  generally  guided  by  the 
severity  of  the  symptoms.  After  other  means  have  been  faithfully 
tried  and  failed,  esophoria  of  more  than  10  degrees  will  at  times 
demand  surgical  interference.  Prisms  of  more  than  4  degrees  in 
each  eye  cannot,  as  a  rule,  be  comfortably  worn.  Moreover, 
prisms  are  changeless  and  constant  in  their  refraction,  while  the 
muscular  conditions  of  the  eyes  are  changing  and  inconstant. 
We  are  attempting  to  correct  a  live  physiologic  function  by  means 
of  a  dead,  unalterable  piece  of  glass.  The  degree  of  esophoria 
varies  as  above  stated — in  fact,  different  estimates  may  be  reached 
by  different  observers  at  the  same  examination,  therefore,  allow- 
ance for  this  variance  must  be  made  in  the  prism  correction. 
After  operation  and  consequent  reduction  of  the  degree  of  esoph- 
oria the  conditions  are  often  more  amenable  to  prism  treatment. 

Should  the  operation  be  limited  to  one  eye  or  should  both  be 
included?  We  are  dealing  either  with  excessive  convergence 
or  defective  divergence,  and  in  either  case  we  have  to  do  with 
more  than  one  muscle  and  more  than  one  eye.  Theoretically, 
therefore,  the  operation  should  be  divided  between  the  two  eyes, 
unless  we  have  reason  to  believe  that  the  esophoria  is  the  result 
of  an  organic  muscular  change,  limited  to  one  eye,  or  is  due  to  a 
nebula  of  the  cornea,  to  high-grade  optical  defect,  to  vitreous 
or  lenticular  opacity,  or  to  some  impairment  of  vision,  indicating 
that  the  esophoria  proceeds  from  a  local  cause  and  is  not  the 
result  of  disturbance  of  innervation,  Heterophoria  is  rarely 
met  with  in  cases  where  organic  imperfections  of  one  eye  lead  to 


124 


FUNCTIONAL   ANOMALIES. 


manifest  squint,  and  usually  to  amblyopia  of  high  degree,  and 
may  therefore  be  excluded  from  consideration  in  this  chapter. 
We  are  concerned  with  patients  who  suffer  from  no  incurable 
affection  of  vision,  have  no  organic  lesion  that  can  be  determined, 
and  who  have,  as  a  rule,  fair  acuity  of  vision  in  both  eyes.  We 
cannot,  therefore,  admit  that  the  tendency  of  the  visual  lines  in- 
ward is  a  monocular  affection  and  that  its  treatment  is  conse- 
quently monocular.  In  all  cases  both  eyes  should  be  made  to 
share  the  treatment  as  nearly  as  possible.  Where  double  opera- 
tion does  not  seem  to  be  indicated,  the  symptoms  can  be  relieved 
by  the  other  means  suggested  without  operation.  It  is  a  debatable 
point  whether  both  eyes  should  be  operated  on  at  the  same  sitting 
or  the  second  operation  follow  several  days  after  the  first.  The 
points  in  favor  of  the  former  are,  that  under  antisepsis  the  surgical 
procedure  is  free  from  danger;  the  incision  is  extremely  small, 
involving  but  few  tissues  and  these  are  superficial;  the  pain  is 

insignificant  and  confined  to  the  drag- 
ging forward  (either  by  the  hook  or 
forceps)  of  the  tendon  and  the  cutting 
of  its  fibers;  hemorrhage  is  unworthy 
of  mention,  the  subsequent  discomfort 
is  little  if  any  more  after  the  double 
operation,  the  rotation  of  each  ball  is 
similarly  and  contemporaneously  in- 
fluenced; and  finally  the  patient  is 
gratified  that  the  performance  is  com- 
pleted. The  advantages  of  the  single  operation  are:  less 
immediately  subsequent  annoyance;  and  the  possibility  that 
it  will  suflice  for  a  cure.  But  such  advantages  are  not  worthy 
of  serious  consideration  when  compared  with  those  of  the  dual 
operation.  The  progress  of  the  operation  must  be  marked 
by  measurement  of  eft'ect  according  to  the  change  in  position 
of  the  images  of  the  candle-flame  at  20  feet  or  of  the  streak 
if  the  Maddox  rod  is  used.  As  often  as  necessary,  the  operation 
must  be  suspended  and  the  result  of  the  section  of  a  few  fibers 
determined,  otherwise  the  operator  is  in  the  dark  and  his  result  is 


Fig.  52. 


ESOPHORLA. 


125 


only  approximate.  In  performing  this  operation  it  is  well  after 
dividing  the  conjunctiva  to  pick  up  the  tendon  of  the  internus  with 
a  forceps  instead  of  a  strabismus  hook  and  simply  button-hole  it 
(Fig.  52).  Further  cautious  divisions  may  be  made  above  and 
below  according  to  the  indications  furnished  by  the  Maddox  rod. 


Vo/fCR.A£f£    J 86 1. 


I^x 


VmGRA£F£  186/. 


ABADIE. 


ZIEGLER. 


1880 


K 


STEVENS.       1883. 


189/. 


VERHOEFE       18  93. 


TODD. 


1907. 


Fig. 


53-- 


-Various    methods    of    doing    partial    tenotomy. 
Ophthalmology,  April,   1911-) 


(Ziegler,     Annals    of 


In  this  way  every  fraction  of  result  secured  from  the  division  of 
even  a  few^  fibers  may  be  most  accurately  studied,  and  overefTect 
avoided.  In  Fig.  53  various  methods  of  doing  partial  tenotomy 
are  portrayed.  Our  own  preference  is  for  the  method  of  Stevens, 
although  that  of  Ziegler  has  much  to  commend  it. 


EXOPHORIA, 


For  a  long  time  it  was  held  that  exophoria  was  a  purely  passive 
condition  resulting  from  diminution  of  the  convergence  impulse, 
but  this  conception  must  now  be  modified.  That  a  certain  per- 
centage of  all  cases  of  exophoria  does  represent  a  passive  or  under 
action  phenomenon  (in  reality  an  accommodative  exophoria)  is  a 
thoroughly  established  fact.  On  the  other  hand,  in  a  series  of  441 
cases  of  exophoria^  it  was  shown  that  in  72  per  cent,  of  the  cases 
there  was  an  associated  H  +  Ah  refractive  status;  and  inasmuch 
as  all  hypermetropic  conditions  call  for  excessive  accommodation 
impulse  (hence  associated  excessive  convergence)  some  factors 
other  than  subnormal  accommodative  impulse  must  be  invoked 
to  explain  this  association.  Moreover,  the  term  exophoria 
(like  esophoria)  while  of  great  clinical  convenience,  is  not  alto- 
gether sufficient  to  the  purpose  for  which  it  is  employed,  in  that 
it  gives  no  clew  as  to  whether  convergence  be  deficient,  divergence 
excessive,  or  both  divergence  and  convergence  deficient. 

For  purposes  of  study,  therefore,  exophoria  may  be  arranged  in 
four  classes : 

1.  Exophoria  with  subnormal  accommodative  power  (generally 
allied  with  an  M  +  Am  refractive  status,  the  old  classic  conver- 
gence insufficiency  of  Donders,  von  Grsefe  and  Landolt). 

2.  Exophoria  (in  the  presence  of  H  -fAh)  with  normal  diver- 
gence and  deficient  convergence. 

3.  Exophoria  (in  the  presence  of  H-f  Ah)  with  normal  con- 
vergence and  divergence  excess. 

4.  Exophoria  (in  the  presence  of  H-j-Ah)  with  convergence 
and  divergence  both  deficient. 

Concerning  exophoria  with  subnormal  accommodative  power 
it  may  be  said  that  the  cause  is  a  myopic  error  of  refraction.     In 

'  Journal  of  the  American  Medical  Association,  1906. 

126 


EXOPHORIA.  127 

myopia  and  myopic  astigmatism  of  two  or  more  diopters,  the 
demand  on  the  accommodation,  when  reading  or  otherwise 
using  the  eye  at  the  usual  near  point,  is  less  than  in  lower 
errors  of  refraction,  since  the  lens,  already  too  convex  to  bring 
parallel  rays  of  light  to  a  point  on  the  retina,  is  adapted  for 
a  distance  inside  of  infinity,  and  the  higher  the  myopia, 
the  nearer  to  the  eye  is  its  far  point,  therefore  the  less  need 
for  contraction  of  the  ciliary  muscle.  The  muscles  of  conver- 
gence, deprived  of  the  impulse  associated  with  ciliary  contraction, 
are  handicapped  and  respond  to  the  impulse  to  convergence  only, 
instead  of  the  impulse  to  convergence  and  accommodation. 
When  we  consider  that  vision  at  the  reading  distance  is  de- 
manded by  the  majority  of  the  human  family  hundreds 
of  times  daily,  the  final  effect  of  such  an  insufficient  innervation 
may  be  readily  appreciated.  After  months  or  years  a  distinct 
loss  of  impulse  results  and  exophoria  appears.  According  to  this 
reasoning  the  degree  of  exophoria  has  a  distinct  ratio  to  the  grade 
of  myopia,  and,  other  things  being  equal,  this  is  the  true  state 
of  the  case.  Indeed,  it  is  rare  to  find  equilibrium  of  the  ocular 
muscles  and  still  rarer  to  find  esophoria  among  myopes,  for  the 
same  reason  that  esophoria  is  common  among  hyperopes. 

Symptoms. — Patients  with  exophoria  are  quite  likely  to  be 
neurasthenic  to  a  greater  or  less  degree,  so  that  their  description 
of  all  their  symptoms  is  subject  to  a  certain  discount. 

Headache. — Naturally  this  is  the  predominant  symptom, 
especially  when  it  persists  after  wearing  a  good  correction.  An 
analysis  of  the  headaches  complained  of  by  173  exophorics  shows 
that  the  frontal  type  was  present  in  102,  the  occipital  type  in 
60  and  the  temporal  type  in  11.  These  headaches  are  more  or 
less  constant,  exist  independently  of  use  of  the  eyes  for  near 
work,  and  are  exaggerated  by  near  work,  also  anything  which 
calls  for  much  quick  adjustment  of  the  eye  muscles,  such  as 
railway  and  trolley  journeys,  moving  in  a  crowd,  and  shopping. 
On  the  other  hand,  anything  which  calls  for  prolonged  steady 
fixation,  such  as  attendance  at  the  theatre  or  gazing  fixedly  at  the 
preacher  in  his  pulpit,  produces  the  same  effect.     Particularly 


128  FUNCTIONAL  ANOMALIES. 

trying  to  such  patients  is  an  expedition  to  a  picture  gallery,  as  the 
gaze  is  generally  directed  upward  and  exophoria  has  a  tendency 
to  become  greater  as  the  eyes  are  turned  upward. 

Of  200  exophorics  in  private  practice,  140  gave  testimony  as  to 
more  or  less  vertigo,  especially  after  near  work.  This  particular 
vertigo  may  not  be  greatly  annoying  as  it  is  of  the  most  transient 
character,  but  the  patient  so  seldom  associates  the  symptoms 
with  their  ocular  status  that  it  will  be  elicited  only  by  questioning. 
Ocular  fatigue  was  present  in  153  of  the  200  cases,  ocular  tender- 
ness in  98,  conjunctival  irritation  in  121,  and  low  grade  photopho- 
bia (or  glarophobia)  was  in  evidence  in  130.  Nausea  of  a  tran- 
sient kind  seemed  fairly  well  related  to  the  exophoria  seventy-two 
times  and  drowsiness  after  near  work,  especially  at  night,  was  almost 
a  constant  symptom.  In  twenty-three  cases  gastric  reflexes  were 
admitted.  By  this  is  meant  a  nameless  vacant  sensation  in  the 
epigastric  region.  That  a  certain  percentage  of  exophorics  (who 
overcome  their  exophoria)  have  this  reflex  is  indisputable.  Two 
cases  presented  intractable  superior  dental  neuralgia  (with  teeth  in 
perfect  condition)  that  yielded  to  treatment  for  the  associated 
exophoria.  It  will,  therefore,  be  seen  that  the  symptoms  are 
variable  indeed,  and  just  as  with  an  uncorrected  refractive  error, 
they  may  be  direct  or  remote,  and  may  be  almost  individual  or 
may  appear  in  groups. 

Diagnosis.  Diplopia  Tests. — A  prism  of  8  degrees  is  placed 
base  down  before  the  right  eye,  the  patient  gazing  at  a  candle 
flame  20  feet  distant.  The  upper  image  is  the  false  one  and  be- 
longs to  the  right  eye.  It  is  not  directly  above  the  true  image, 
but  is  above  and  to  the  left.  The  prism  base  in  before  either  eye 
that  brings  the  two  images  directly  in  a  vertical  line  is  the  measure 
of  the  exophoria.  The  phorometer  of  Stevens  is  a  much  readier 
application  of  the  same  principle,  and  by  rotation  of  its  lever  the 
character  and  amount  of  the  exophoria  are  shown  at  once. 

Cobalt  Glass  Test. — In  high-grade  exophoria,  diplopia  will  be 
produced  by  holding  a  cobalt  blue  glass  in  front  of  one  eye,  the 
image  seen  by  which  will  be  blue-red  and  smaller  than  that  seen 
by  the  uncovered  eye;  the  cobalt  image  will  lie  on  the  side  opposite 


EXOPHORIA.  129 

to  the  eye  before  which  the  glass  is  placed,  the  separation  depend- 
ing on  the  grade  of  exophoria,  expressed  in  terms  of  the  prism, 
base  in,  necessary  to  fuse  the  cobalt  and  the  true  image.  Defects 
of  less  than  3  degrees  are,  as  a  rule,  not  uncovered  by  this  test. 

Distorting  Tests. — Of  most  value  is  the  Maddox  multiple  rod. 
If  it  is  so  placed  before  the  right  eye  in  the  trial  frame  that  a 
vertical  streak  appears  before  that  eye,  the  streak  will  fall  to  the 
left  of  the  candle  flame;  and  to  the  right  if  the  rod  is  placed  before 
the  left  eye;  that  is,  the  images  are  crossed.  The  prism  base  in 
before  either  eye  that  will  displace  or  carry  the  streak  directly 
through  the  flame  represents  the  degree  of  the  defect. 

Cover  and  Parallax  Test. — The  patient  gazes  at  a  small  brilliant 
object  20  or  more  feet  distant.  The  eyes  are  screened  alternately, 
thus  breaking  up  fusion.  As  the  cover  or  screen  is  carried  back 
and  forth  from  one  to  the  other  eye,  the  uncovered  eye  will  move  in 
toward  the  median  line  because  while  under  the  cover  it  has  rolled 
out  into  the  position  most  restful  for  it.  The  prism  base  in  before 
either  eye  that  will  arrest  the  movement  of  the  eyes  is  the  measure 
of  the  exophoria.  This  test  is  wholly  an  objective  one  and  its 
objectivity  and  accuracy  give  it  great  value.  It  does  not  consume 
more  than  one  minute  in  its  application  and  should  never  be 
omitted  from  the  study  of  any  case  of  exophoria.  If  it  is  desired 
to  make  it  subjective  by  asking  the  patient  after  a  few  movements 
with  the  card  whether  the  fixation  object  appears  to  jump  from 
side  to  side  as  the  card  is  shifted  this  is  readily  done,  and  so  carried 
out  becomes  the  parallax  test.  The  prism  base  in  before  either 
eye  that  arrests  the  apparent  jump  of  the  fixation  object  is  the 
measure  of  the  deviation.  This  test  is  of  the  greatest  delicacy, 
one-fourth  of  a  degree  of  deviation  being  easily  possible  of  de- 
tection in  intelligent  patients. 

Tests  for  the  Reading  Distance. — In  no  class  of  cases  will  tests  at 
the  reading  distance  be  more  serviceable  than  in  exophoria. 
For  this  purpose  we  have  discarded  the  dot  and  line  test,  and  use 
almost  entirely  the  multiple  Maddox  rod  and  a  small  one  candle 
electric  light.  The  patient  holds  the  light  at  the  ordinary  read- 
ing distance  (about  13  inches)  and  the  state  of  the  muscles  at 
9 


130  FUNCTIONAL  ANOMALIES. 

that  point  is  estimated,  the  patient's  correction  invariably  being 
worn-  during  the  test.  In  presbyopes  the  reading  correction 
should  be  used  when  the  test  is  applied  or  the  observer  may  be 
led  into  error.  S-child's,  Baer's  or  any  other  modification  of 
the  apparatus  just  described  may  be  used. 

Too  much  stress  cannot  be  laid  on  this  test  in  exophoria,  as  is 
illustrated  by  the  following  fairly  typical  case: 

J.  G.,  thirty-five,  accountant,  complains  much  of  ocular  dis- 
tress after  working  two  to  three  hours  consecutively  over  accounts. 
He  had  been  carefully  refracted  three  months  previously  and 
ordered  a  suitable  correction.  At  that  time  exophoria  of  i 
degree  for  infinity  had  been  noted.  Estimation  of  the  muscle 
status  at  his  working  distance  revealed  exophoria  of  11  degrees 
and  no  hyperphoria.  The  convergence  near  point  was  5  inches 
(12  1/2  centimeters).  The  abduction  was  8  degrees  and  the 
adduction  12  degrees.  He  was  given  convergence  training  which 
improved  the  condition  somewhat.  Finally  a  i  degree  prism 
base  in  each  eye  was  incorporated  in  his  regular  correction  and 
this  prismatic  glass  ordered  for  his  work  at  accounts  only. 
Within  four  weeks  all  his  ocular  distress  had  disappeared. 

Supplementary  Tests.  Prism  Cofivergence. — As  has  been 
noted  in  a  previous  chapter,  prism  convergence  is  such  a  vari- 
able factor  that  it  may  prove  misleading  if  too  much  reliance  is 
placed  upon  it.  Yet  it  will  often  elicit  some  interesting  informa- 
tion and  should  be  estimated  in  all  obscure  cases.  In  general 
terms  there  should  be  at  least  twice  if  not  three  times  as  much 
prism  convergence  as  prism  divergence  in  all  but  high  degrees  of 
exophoria. 

Prism  Divergence. — Prism  divergence  is  commonly  a  com- 
paratively fixed  quantity  and  if  found  to  be  6  or  8  or  9  degrees  at 
any  one  sitting  it  is  fairly  sure  to  measure  the  same  at  any  future 
sitting.     It,  therefore,  becomes  a  factor  of  marked  value.     Usu- 
ally it  is  not  found  to  be  more  than  the  normal  7  degrees. 

The  Convergence  Near  Point. — In  every  case  of  exophoria 
this  element  is  of  paramount  importance,  Landolt  many  years 
ago  devised  for  the  ready  estimation  of  the  convergence  near  point 


EXOPHORIA.  131 

his  ophthalmodynamometer  (see  page  106)  which  is  of  much 
service.  For  the  last  eight  years  we  have  employed  for  the  same 
purpose  the  tiny  electric  light  of  the  De  Zeng  electric  ophthal- 
moscope. With  the  room  half  darkened,  and  starting  at  15 
inches  from  the  face,  the  patient  watches  the  light  attentively  as 
it  is  carried  in  the  median  line  closer  and  closer  to  the  face.  At 
about  10  inches  from  the  eyes  the  bright  small  corneal  images 
from  the  electric  light  become  plainly  visible  to  the  surgeon  and  it 
is  easy  to  watch  the  behavior  of  these  images  as  the  light  is  carried 
toward  the  root  of  the  patient's  nose  until  one  or  the  other  of  the 
corneal  images  shows  that  the  eye  to  which  it  belongs  is  no  longer 
being  converged.  This  is  the  near  point  of  convergence  and  one 
can  thus  readily  calculate  the  number  of  meter  angles  of  positive 
convergence  at  the  patient's  disposal.  For  instance,  if  the  eyes 
refuse  to  converge  inside  of  4  inches  there  are  10  meter  angles  of 
positive  convergence;  if  they  refuse  at  5  inches  there  are  8  meter 
angles;  if  at  3  inches  there  are  13  meter  angles.  The  test  as  thus 
applied  is  objective,  while  Landolt's  proceeding  is  subjective  and 
open  to  all  the  disadvantages  of  every  subjective  test;  it  is 
rapidly  applied  and  of  proven  value.  If  we  now  divide  the 
prism  divergence  (previously  estimated)  by  7  and  add  the 
quotient  to  the  positive  convergence  we  shall  have  the  total 
amplitude  of  convergence.  Usually  the  average  patient  has 
from  I  to  I  I  /2  meter  angles  of  negative  convergence  (prism 
divergence)  hence  the  calculation  becomes  very  easy.  Thus: 
Fannie  G,  aged  eighteen,  shows  3  degrees  of  exophoria  for  dis- 
tance and  15  degrees  for  the  reading  distance.  Her  prism 
divergence  is  7  degrees  (equals  i  meter  angle  of  convergence) 
and  her  convergence  near  point  equals  8  inches — that  is, 
meter  angles  of  positive  convergence.  Hence  her  total  amplitude 
of  convergence  is  but  5  positive  and  i  negative  or  total  6  meter 
angles.  Inasmuch  as  anyone  who  wishes  to  use  his  eyes  much 
at  the  reading  distance  should  have  at  least  1 1  meter  angles  of 
convergence  amplitude  (that  is  to  say  a  convergence  near  point 
of  at  least  4  inches)  it  is  needless  to  say  that  this  young  woman  had 
great  difficulty  in  using  her  eyes  for  any  reading,  writing  or 


132  FUNCTIONAL  ANOMALIES. 

sewing.  In  some  cases  of  exophoria,  the  tropometer  will  be  of 
value  in  determining  whether  both  eyes  share  equally  in  the 
deviation  (innervational  exophoria)  or  whether  one  eye  is  mark- 
edly deficient  in  its  adducting  power  as  compared  with  the  other 
(anatomic  exophoria). 

The  four  principal  tests  in  the  study  of  all  exophorias  are : 
a.  the  exophoria  for  infinity  (or  distance) ;  b.  the  prism  divergence; 
c.  the  exophoria  at  the  reading  distance,  and  d.  the  convergence 
near  point.  There  are  many  supplementary  tests  that  may  be 
used  to  advantage,  but  knowledge  of  the  four  facts  just  mentioned 
is  essential  for  the  proper  treatment  of  any  case  of  exophoria. 

In  all  cases  of  exophoria  the  various  tests  should  corroborate 
each  other  closely,  in  which  case  no  difficulty  should  be  experi- 
enced in  arriving  at  the  conclusion  that  the  visual  axes  have  a  ten- 
dency away  from  each  other.  Here  again,  much  as  in  esophoria, 
we  are  dealing  with  the  relation  between  divergence  and  conver- 
gence and  (with  the  exception  of  the  anatomic  cases)  not  with  the 
externus  or  internus  of  one  or  both  eyes,  but  with  the  diverging 
power  of  the  externi  and  the  obliques  as  opposed  to  the  converg- 
ing power  of  the  interni,  assisted  by  the  vertical  recti. 

Finally,  no  test  for  exophoria  is  reliable  that  is  instituted  any 
time  within  twenty-four  hours  of  the  time  that  a  mydriatic  is 
used  in  the  eyes  for  the  same  reasons  set  forth  in  the  chapter  on 
Esophoria.  Tests  should  be  made  before  the  mydriatic  is  used, 
and  if  with  the  mydriatic  effect  in  the  eyes  not  until  the  mydriatic 
has  been  exerting  a  constant  effect  for  two  to  three  days. 

Treatment. — The  treatment  of  exophoria  (or  latent  diver- 
gence) calls  for  much  discrimination. 

I.  As  most  of  such  patients  are  more  or  less  neurasthenic 
(as  has  been  already  pointed  out),  too  much  emphasis  cannot  be 
laid  upon  the  value  of  right  living.  This  implies  moderation 
in  all  things  (including  diet,  smoking,  drinking  and  all  other 
daily  life  habits).  Hydrotherapy,  either  by  means  of  warm  baths 
before  retiring  or  a  quick  cold  sponge  on  arising — preferably  the 
latter— is  often  of  service.  An  additional  hour  or  two  of  sleep  will 
at  times  prove  the  saving  measure. 


EXOPHORIA.  133 

2.  The  Correction  of  the  Error  of  Refraction. — This  reiteration 
may  become  wearisome,  but  the  authors  concede  that  the  great 
proportion  of  muscular  insufficiencies  are  directly  or  indirectly 
originated  by  ametropia,  and  believe  they  would  be  remiss  in 
their  duty  unless  they  insisted  on  every  opportune  occasion  that 
treatment  should  be  invariably  inaugurated  by  correction  of  any 
optical  defect  that  may  be  present,  for  the  double  reason  that  the 
optical  defect  may  be  the  sole  source  of  the  muscular  symptoms  and 
its  correction  may  prove  the  cure  of  the  same;  further,  no  restoration 
to  equilibrium  can  be  expected  when  the  cause  thereof  is  acting. 
In  exophoria  associated  with  H  +  Ah  it  is  the  part  of  wisdom  to 
undercorrect  the  spherical  element  of  the  refractive  error  by 
anywhere  from  +0,50  to  +  i.oo  sphere  according  to  the  degree  of 
the  deviation.  This  extra  stimulus  to  the  accommodation  will 
serve  a  good  purpose  in  evoking  extra  stimulus  to  the  conver- 
gence, the  thing  most  needed  in  latent  divergence. 

For  the  same  reason  we  encounter  the  accommodative  variety 
of  exophoria  in  M  + Am,  The  explanation  is  found  in  the  incom- 
plete or  altogether  neglected  use  of  the  accommodation.  The 
myopic  eye  has  a  far  point  inside  of  infinity,  its  distance  from  the 
eye  depending  upon  the  diopters  of  myopia.  Thus  in  M.  of  3 
diopters  the  far  point  is  13".  This  is  a  convenient  distance  for 
reading  and  no  accommodation  is  required.  In  M.  of  5  diopters, 
the  far  point  is  8'',  which  is  too  near  for  the  exercise  of  accommo- 
dation. In  such  cases,  therefore,  convergence  is  deprived  of  the 
usual  associated  stimulus  of  the  ciliary  muscle,  and  gradually 
weakens.  It  can  be  readily  seen,  therefore,  that  in  the  presence  of 
myopia  the  correction  of  the  refraction  is  a  necessary  part  of  the 
treatment  of  the  muscular  anomaly.  Indeed,  when  the  myopia  is 
not  too  high  or  the  patient  too  old,  it  is  often  the  only  treatment 
demanded.  The  correction,  in  order  to  be  effective,  should  be 
worn  constantly. 

If,  after  two  months'  use  of  proper  correcting  glasses  muscular 
equilibrium  is  not  restored  or  the  symptoms  persist,  medicinal 
treatment  may  be  resorted  to. 

3.  Nerve  Tonics. — The  remedy  that  has  been  most  warmly 


134  FUNCTIONAL  ANOMALIES. 

endorsed  and  that  the  authors  ha\'e  found  extremely  serviceable 
is  tincture  of  nux  vomica  in  ascending  doses.  Strychnin,  the 
alkaloid  of  nux  vomica,  is  for  some  reason  less  eflficient.  The 
beginning  dose  of  the  tincture  should  be  20  drops  thrice  daily, 
increasing  the  dose  one  drop  every  day  until  50  to  60  drops  thrice 
daily  are  taken  or  until  symptoms  of  physiologic  action  of  the 
drug  appear.  Then  the  dose  is  similarly  decreased  day  by  day 
until  the  original  dose  is  reached,  vv^hen  the  drug  may  be  with- 
dravi^n.  The  measure  that  is  of  most  service  in  connection  with 
the  use  of  nux  vomica  is  training  of  the  convergence  faculty  by 
means  of  prisms. 

4.  Convergence  Training. — This  may  be  of  various  kinds. 
We  resort  mainly  to  tv^^o  methods.  First,  converging  exercises 
with  a  pencil  point  held  at  arms  length;  this  is  carried  in  toward 
the  root  of  the  nose  until  the  patient  sees  double  when  the  eyes  are 
closed  and  the  pencil  carried  back  to  arms  length  and  the  move- 
ment repeated  up  to  ten  to  twenty  times.  Such  an  exercise  period 
should  be  gone  through  two  or  three  times  a  day.  In  this  way 
the  convergence  near  point  can  be  brought  nearer  and  nearer  and 
the  positive  range  of  convergence  much  increased.  The  same 
exercise  to  the  right  and  left  is  sometimes  helpful. 

The  range  and  power  of  convergence  can  be  distinctly  increased 
by  regular  prism  exercise.  Prisms,  bases  out,  have  been  used  in 
various  ways  by  different  workers  for  many  years  for  the  exercise 
of  the  adduction;  Risley,  Michel,  Savage,  Noyes,  Gould  and  others. 
(Acknowledgement  is  gratefully  made  by  the  senior  author  to  his 
friend  and  preceptor.  Dr.  Wm.  Thomson,  until  lately  Emeritus 
Professor  of  Ophthalmology  in  the  Jefferson  Medical  College, 
for  instruction  nearly  thirty  years  ago  in  his  ofifice,  in  the  use  of 
prisms  both  as  a  method  of  stimulating  the  innervational  force  of 
the  external  ocular  muscles  and  as  a  means  of  relief  in  muscular 
asthenopia).  The  battery  of  Noyes  or  Gould  is  a  convenient 
arrangement  of  prisms  and  can  be  employed  with  benefit,  although 
the  costliness  of  such  apparatus  limits  its  use  to  the  consulting 
room.  For  home  use  the  prisms  are  to  be  mounted  either  in  an 
ordinary   spectacle   frame   or  in   one   of   the   numerous  frames 


EXOPHORLA. 


135 


specially  devised  for  carrying  square  prisms  so  that  they  may  be 
increased  ad  libitum.  (See  Fig.  53a).  The  patient  is  given  a 
pair  of  5  degree  prisms  in  the  frame,  with  which  he  walks  toward 
a  candle  flame  placed  at  the  opposite  side  of  the  room.  The 
prisms  arc  not  looked  through  as  he  goes  toward  the  light,  but 
are  raised.  As  soon  as  he  approaches  within  2  feet  of  the  light 
the  prisms  are  dropped  before  the  eyes  and  he  backs  away  from 
the  light  gazing  steadily  at  it  all  the  time.  Should  the  light 
appear  double  any  time  while  he  is  backing  across  the  room,  the 
patient  immediately  raises  the  prisms,  walks  toward  the  light 
again  and  backs  away  with  the  prisms  before  the  eyes  until  he 


Fig.  53a. — Training  prisms  for  exophoria. 

can  go  the  whole  length  of  the  room  without  seeing  the  candle 
double.  This  is  done  from  ten  to  fifteen  times  two  or  three  times 
a  day.  After  two  weeks  10  degree  prisms  are  ordered  to  be  used 
in  the  same  way  and  after  another  fortnight  15  degree  or  20 
degree  prisms  according  as  the  patient  learns  rapidly  or  slowly  the 
trick  of  dissociating  his  accommodation  and  convergence.  There 
is  a  class  of  patients  for  whom  convergence  training  as  above 
described  is  particularly  indicated;  namely,  the  exophorics  who 
present  but  i  or  2  degrees  of  deviation  for  infinity  with  anywhere 
from  10  to  15  degrees  of  deviation  at  the  reading  distance  (prism 
divergence  being  normal).  These  patients  respond  finely  to 
convergence  training  as  a  rule.  It  will  often  require  the  strictest 
injunctions  on  the  part  of  the  surgeon  to  impress  upon  the  patient 
the  necessity  for,  and  the  importance  of  these  calisthenics,  and 
to  bring  him  to  realize  that  the  partial  or  complete  relief  of  his 
asthenopia  is  largely  in  his  own  hands.  The  cooperation  of  the 
patient  once  secured,  the  prisms  can  be  rapidly  increased  in 
strength  and  the  fusion  force  often  carried  to  100  degrees  of  prism 
inside  of  eight  or  twelve  weeks,  in  which  event  the  patient  is 


136  FUNCTIONAL   ANOM.'\LIES. 

pretty  sure  to  have  experienced  marked  relief  from  the  asthenopia. 
The  main  difliculty  in  this  method  lies  in  the  persistence 
necessary  to  convince  the  patient  that  little  is  to  be  hoped  for 
without  the  heartiest  cooperation.  Many  cases  of  severe 
muscular  asthenopia  can  be  made  quite  comfortable  by  the 
combined  action  of  increasing  doses  of  nux  vomica  and  prism 
exercise;  indeed,  their  value  has  been  universally  acknowledged. 
An  interesting  clinical  fact  in  connection  with  this  method  of 
treatment  is  that  if  a  patient  start  with  an  exophoria  of  10  de- 
grees for  distance  and  18  degrees  for  15  inches,  (the  occupation 
distance),  the  asthenopic  symptoms  may  be  entirely  dissipated  by 
nux  vomica  and  prism  exercise  for  two  or  three  months,  not- 
withstanding which  the  exophoria  for  distance  will  remain  at 
10  degrees,  while  that  for  near  may  have  fallen  to  3  degrees  or  5 
degrees,  or  have  entirely  disappeared;  all  of  which  goes  to  show 
that  exercise  of  the  adduction  may  increase  the  range  of  conver- 
gence (as  can  be  found  by  prism  tests  of  the  adduction  and  abduc- 
tion), but  will  seldom  influence  to  any  extent  the  muscle-balance 
for  20  feet.  In  other  words,  we  have  simply  made  easy  to  the 
patient  a  much-needed  coordination,  and  have  perhaps  at  the 
same  time  trained  the  cortical  fusion  centers  to  a  higher  degree 
of  efficiency.  These  measures  are  peculiarly  useful  in  individuals 
who  have  passed  through  a  debilitating  illness,  such  as  typhoid 
fever,  la  grippe,  measles  or  diphtheria;  also  in  young  and  growing 
subjects,  and  their  action  is  always  enhanced  by  life  in  the  open 
air,  general  muscular  exercise  and  nutritious  diet.  Occasional 
cases  will  be  met  with  whose  symptoms  are  decidedly  aggravated 
by  prism  training.  This  is  frequently  a  clinical  indication  for 
the  use  of  prisms  permanently  in  the  position  of  rest  in  the  patient's 
glasses. 

5.  Prism  Correction. — When  the  symptoms  of  exophoria  are 
not  relieved  by  the  preceding  measures  and  are  of  such  a  severity 
that  relief  can  be  obtained  only  by  relaxation  (or  easing)  of  con- 
vergence, the  wearing  of  prisms  in  the  position  of  rest  is  to  be  con- 
sidered (Fig.  54).  The  use  of  prisms,  bases  in,  to  be  incorporated 
in  the  patient's  distance  correction  has  been  deprecated  by  many 


EXOPHORIA. 


137 


authorities  who  contend  that  exophoria  for  iniinity  increases  under 
the  constant  wear  of  such  prisms;  furthermore,  that  they  do  not 
cure  the  deviation,  but  only  relieve  the  symptoms.  That  this  is  true 
within  certain  limits  must  be  admitted;  and  yet  when  correction 
of  the  ametropia  has  failed  to  relieve,  and  attempts  at  training 
the  convergence  have  been  poorly  borne  the  trial  of  prisms  bases 
in  in  an  extra  or  hook  front  experimentally  seems  justifiable.  In 
properly  selected  cases  it  will  be  found  that  when  convergence  has 
been  made  somewhat  easier  for  the 
patient  by  the  use  of  rest  prisms,  the 
convergence  may  then  be  trained  to 
a  very  considerable  point  and  the 
exophoria  for  infinity  thus  kept  from 
increasing.  This  was  our  experience 
in  seventeen  out  of  forty-two  cases 
in  which  prisms  bases  in  were  ordered 
for  constant  use.  If  the  exophoria 
is  the  result  of  a  temporary  loss  of 
convergence  from  overuse  of  the  eyes 
or  exhaustion  of  the  nervous  system 
the  prisms  not  only  give  comfort,  but 
they  may  gradually  be  reduced  in 
strength  and  finally  discarded. 
While  the  prisms  are  worn  the 
visual  axes  diverge  and  the  globes 
assume  that   position    in    the    orbit 

most  restful  for  them.  The  effort  of  convergence  is  partially  in 
abeyance  and  the  strain  of  opposing  the  power  of  divergence  is 
relaxed.  The  eyeballs  are  diverged  and  single  vision  is  maintained 
by  the  prisms.  For  these  reasons  it  is  good  practice  to  allow  a 
goodly  proportion  of  the  exophoria  to  remain  uncorrected  by 
prescribing  prisms  that  permit  constant  but  limited  use  of  con- 
vergence. Thus,  in  exophoria  of  8  degrees  for  infinity,  prisms 
of  I  to  2  degrees  before  each  eye  may  be  tried.  It  is  well  to  feel 
one's  way  with  prisms,  the  purpose  in  view  being  not  to  supplant 
convergence,  but  simply  to  ease  it  up.    Whether  the  prisms  should 


Fig.  54. — Effect  of  converging 
prisms  in  exophoria. 


138  FUNCTIONAL   ANOMALIES. 

or  should  not  be  worn  constantly  depends  upon  the  symptoms 
accompanying  the  use  of  the  eyes  for  distance.  Defects  of  4 
degrees  and  less  for  20  feet  rarely  require  their  use.  Higher 
defects  will  usually  demand  their  constant  use.  There  is  a  limit, 
however,  to  the  benefit  to  be  derived  from  prismatic  correction 
according  to  sex,  age,  occupation,  etc.,  but  in  general  terms  the 
highest  degree  of  prism  that  can  be  comfortably  worn  may  be 
placed  at  5  degrees  before  each  eye. 

6.  Prism  Correction  for  the  Reading  Distance. — In  certain  cases 
of  exophoria  it  is  at  times  sufficient  to  employ  prisms  in  connec- 
tion with  the  reading  or  occupation  glasses  only.  This  is  espe- 
cially true  in  presbyopic  exophorics.  The  influence  of  age  in 
unmasking  or  perhaps  even  developing  exophoria  is  unmistak- 
able.    Reference  to  the  accompanying  table 

TABLE  E. 

Decade.  .         /       ,  Decade.  .         .'       , 

times  found.  times  found. 

Under  lo 6            41  to  5c 124 

1 1  to  20 34             5 1  to  60 59 

211030 go             611070 14 

31  to  40 106             Over  70 6 

setting  forth  an  analysis  of  the  incidence  of  exophoria  in  the 
various  decades  of  life  will  show  that  the  decade  from  forty  to 
fifty  presents  the  greatest  number  of  cases  of  exophoria.  Less 
than  I  /lo  of  all  the  cases  occurred  prior  to  the  20th  year  of  life 
and  over  one-half  of  all  the  cases  in  the  period  between  thirty  and 
fifty  years  of  age.  It  is  not  at  all  uncommon  to  find  presbyopes 
who  reveal  but  i  to  2  degrees  of  exophoria  for  infinity  with  8  to 

12  degrees  for  the  reading  distance.  Prism  training  often  pro- 
duces the  happiest  results  in  such  patients,  but  when  it  fails 
one  need  not  hesitate  to  incorporate  a  i  to  2  degree  prism  base  in 
in  each  lens  (preferably  i  degree)  and  the  effect  is  generally 
most  gratifying.  Decentration  of  the  lenses  will  accomplish  the 
same  result,  but  more  will  be  said  of  this  in  another  place. 

When  all  the  procedures  mentioned  fail  to  afford  relief  we  are 
obliged  to  consider  operation. 


EXOPHORLA..  139 

7.  Operation. — The  surgeon  has  the  choice  between  tenotomy 
of  the  externi  on  the  one  hand  and  advancement  (with  or  without 
resection)  of  the  interni,  or  of  the  capsule,  on  the  other  hand. 
If  exophoria  depends  upon  lessened  convergence  power,  there 
would  seem  to  be  no  alternative  between  these  two  procedures; 
that  the  choice  must  fall  upon  measures  that  will  strengthen  con- 
vergence rather  than  weaken  divergence.  In  our  own  practice 
tenotomy  of  the  externi  for  exophoria  is  not  often  resorted  to. 
Advancement  is  performed  in  nearly  every  instance.  We  believe 
this  is  correct  practice  founded  upon  sound  physiologic  principles, 
yet  we  are  obliged  to  admit  in  all  fairness  that  our  results  have  not 
always  been  as  satisfactory  as  we  or  our  patients  could  wish. 
Advancement  (capsular  or  capsulomuscular)  is  far  more  difficult 
and  tedious  to  perform  than  tenotomy,  more  painful  and  incapaci- 
tating to  the  patient  and  it  may  not  increase  the  power  of  con- 
vergence. When  accurately  done  we  believe  it  is  superior  to  and 
gives  more  lasting  results  than  tenotomy.  On  the  other  hand, 
tenotomy  can  be  done  under  local  anesthesia;  it  is  extremely 
simple  and  easy  to  perform,  it  can  be  made  most  accurate,  it 
inflicts  but  little  pain,  and  a  very  short  period  of  incapacity  and 
when  divergence  is  greatly  in  excess  occasionally  affords  brilliant 
results.  In  patients  under  thirty  years  of  age  it  would  generally 
be  best  to  resort  to  advancements;  after  that  time,  when  the 
divergent  forces  are  more  in  evidence,  tenotomy  may  be  considered 
when  divergence  can  be  plainly  shown  to  be  greatly  in  excess  of 
normal.  In  deciding  as  to  operative  treatment,  the  etiologic  relation 
between  exophoria  and  hyperphoria  must  be  constantly  borne  in 
mind.  (See  chapter  on  \'ertical  Imbalance  and  Lateral  Imbalance) . 
Whether  one  or  both  eyes  shall  be  operated  upon  is  to  be  decided 
on  the  merits  of  each  case.  The  effect  in  degrees  gained  by  a 
single  operation  depends  largely  on  the  preserved  power  of  ad- 
duction. As  a  rule,  it  does  not  exceed  5  to  6  degrees  and  when 
more  than  this  amount  of  correction  is  demanded,  as  is  the  case 
in  most  subjects  for  operation,  each  internus  should  be  advanced. 
It  is  true  that  more  effect  in  the  divergence  can  be  obtained  by 
full  tenotomy  of  the  externi  and  at  first  sight  this  operation  would 


I40  FUNCTIONAL   ANOMALIES. 

appear  to  be  indicated,  but  full  tenotomy  of  one  or  both  externi 
should  never  be  done  because  of  the  serious  objection  of  dimin- 
ished external  rotation. 

Moreover,  as  has  been  said,  there  is  not  so  much  promise  of 
permanency  of  result  and  increase  in  adduction  with  tenotomy 
as  with  advancement.  So  that  if  the  surgeon  is  sufficiently 
sure  of  his  technique,  he  will  probably  obtain  the  best  results 
by  operating  on  both  interni,  dividing  the  amount  of  correction 
between  the  two  eyes  (as  nearly  as  may  be),  at  the  same  sitting. 
Postponement  of  the  second  operation  is  not  contra-indicated, 
yet  the  preference  should  be  given  to  the  double  operation  since 
by  this  plan  the  dread  and  anxiety  of  the  patient  are  reduced 
more  than  one-half  and  the  eyes  are  in  a  condition  to  respond 
equally  to  the  innervational  impulse.  If  these  facts  are  explained 
to  the  patient  it  is  improbable  that  he  will  raise  objections  to  the 
plan  proposed,  but  will  submit  philosophically  to  the  reasoning  of 
the  surgeon.  (For  description  of  tenotomy  and  advancement  see 
chapter  on  Operations.) 


HYPERPHORIA 


Hyperphoria  is  that  condition  in  which  there  is  a  tendency  of 
one  visual  line  in  a  direction  above  that  of  the  other.  Hyper- 
phoria (latent  vertical  squint)  differs  from  hypertropia  (manifest 
vertical  squint)  only  in  that  single  vision  is  not  possible  in  the  lat- 
ter condition,  and  the  eye  that  is  more  ametropic,  or  is  at  the 
greater  muscular  disadvantage,  gives  up  the  struggle  and  actually 
deviates  upward  or  downward. 

If  we  accept  the  above  definition,  it  will  be  found  that  hyper- 
phoria is  by  no  means  rare,  nor  is  its  presence  inconsistent,  in 
some  cases,  with  perfect  health  and  comfort  in  using  the  eyes,  in 
which  event  there  can  be  no  excuse  for  treatment  of  the  tendency 
to  deviation. 

An  analysis  of  the  findings  at  the  first  visit  in  700  consecutive 
refraction  cases  occurring  in  our  practice  showed  that  20  per  cent, 
of  all  of  them  revealed  hyperphoria  of  one-half  degree  or  more;  and 
a  recent  study  of  3600  refraction  cases  in  our  private  practice  in- 
dicates 7  per  cent,  in  whom  prolonged  study  of  the  case  revealed  i 
degree  or  more  of  hyperphoria.  Carpenter  found  it  in  35  per  cent, 
of  his  private  cases  at  the  first  consultation,  Posey  in  13  per  cent., 
Bannister  (working  among  the  U.  S.  Navy  recruits)  in  7  per  cent., 
and  Howe  and  Williams  in  16  per  cent.  This  would  indicate  that 
about  one  in  ten  of  all  patients  who  are  the  subjects  of  muscular 
or  accommodative  asthenopia  will  during  the  preliminary  exam- 
ination display  some  degree  of  vertical  imbalance,  either  alone  or 
associated  with  esophoria  or  exophoria.  It  should  ever  be  borne 
in  mind,  however,  that  hyperphoria  (like  esophoria  or  exophoria) 
occurs  in  a  fair  percentage  of  individuals  in  whom  careful  re- 
fraction alone  without  any  special  optical  treatment  of  the  muscle 
status  seems  to  give  perfect  relief.  Some  people  carry  a  vertical 
error  of  i  to  2  degrees  all  through  a  life  of  high  tension  and 
large    usefulness    without    any   particular  discomfort,   while  in 

141 


142  FUNCTIONAL  ANOMALIES. 

Others  one-half  to  three-quarters  of  a  degree  is  sufficient  to  make 
life  a  burden.  Nature  is  marvelously  elastic  in  her  adjustments. 
So  that  the  mere  finding  that  a  patient  has  hyperphoria  is  of 
itself  nothing  until  the  vertical  deviation  is  viewed  in  its  relation 
to  his  or  her  heredity,  environment,  temperament,  occupation, 
physical  condition  and  last,  but  most  important,  the  refractive 
status  of  the  eyes.  Hyperphoria  of  3  degrees  in  a  soldier  may 
easily  prove  a  negligible  quantity;  while  hyperphoria  of  one  to 
one  and  a  half  degrees  in  a  student,  accountant,  stenographer, 
private  secretary,  etc.,  may  alter  their  whole  career.  One  must 
be  on  the  lookout  always  for  spurious  hyperphoria.  The  follow- 
ing case  is  in  point : 

A.  W.,  female,  aged  sixteen.  Comes  on  account  of  difficulty 
in  all  near  work.  General  health  fair.  Vision  R.  E.  5/7;  L.  E. 
5/9.  Accommodation  normal.  Muscle  status  esophoria  4  de- 
grees, left  hyperphoria  2  degrees.  Under  atropia  the  refraction 
status  was 

R.  +0.50  sph= +  1.25  cyl.    75  degrees 
L.  +0.62  sph=  +1.00  cyl.  135  degrees 

after  two  weeks  use  of  the  cylinders  only,  the  hyperphoria  dis- 
appeared nor  was  there  any  in  evidence  i  year  later  when  the  case 
was  studied  again.     Such  cases  are  not  rare. 

This  class  of  cases  (ametropic),  along  with  those  secondary  to 
gout,  rheumatism,  central  nervous  lesions  and  other  general 
diseases,  comprise  what  are  known  as  temporary  hyperphorias  in 
contradistinction  to  true  or  permanent  hyperphorias  which  occur 
independently  of  constitutional  conditions,  and  persist  after  long 
use  of  the  closest  correcting  lenses. 

Symptoms. — The  symptoms  of  hyperphoria  are  ocular  and  re- 
flex.    The  ocular  symptoms  are: 

1.  Chronic  hyperemia  of  the  lids,  often  giving  rise  to  a  condition 
aptly  likened  by  one  writer  to  the  "hot  eye"  of  gout. 

2.  Epiphora,  generally  unilateral  and  seemingly  without  nasal 
or  ocular  cause. 

3.  Defective  Vision. — It  is  not  unusual  to  find  vision  of  but 


HYPERPHORIA.  1 43 

2  JT,  to  I  J2  in  an  hyperphoric  eye  even  after  accurate  correction 
of  a  low-grade  ametropia;  indeed,  it  may  be  impossible  to  give 
each  eye  better  vision  than  5/7,  a  fact  easy  of  explanation,  how- 
ever, if  it  is  borne  in  mind  that  an  actual  vertical  imbalance  of 
I  degree  will  result  in  a  separation  of  images  at  20  inches  of  6  i  /2 
mm.  Such  a  patient,  if  a  worker  at  the  occupation  distance,  will 
most  surely  be  troubled  from  time  to  time, 

4.  Confusion  of  images,  which  is  the  result  of  the  transient 
diplopia.  It  may  be  urged  that  many  students  carry  a  hyper- 
phoria of  I  degree  or  more  through  a  busy  career  extending  over 
many  years  without  experiencing  any  annoying  symptoms 
whatever.  Such  persons  either  possess  a  physical  and  nervous 
system  that  would  weather  any  storm,  or  they  have,  consciously 
or  unconsciously,  learned,  by  carrying  the  head  toward  one  or  the 
other  shoulder,  to  neutralize  their  hyperphoria  wholly  or  in  part. 
This  habit  constitutes  the  fifth  important  symptom  of  true  hy- 
perphoria, namely: 

5.  Carriage  of  the  Head. — The  head  is  usually  tilted  toward  the 
shoulder  opposite  to  the  hyperphoric  eye,  a  statement  that  may 
sound  strange,  but  when  it  is  remembered  that  in  right  hyperphoria 
the  image  is  really  seen  lower  by  the  right  eye,  it  naturally  follows 
that  the  head  must  be  tilted  toward  the  left  shoulder  if  the  images 
are  to  be  brought  to  a  level  and  binocular  vision  thus  rendered  an 
unconscious  act.  Graefe  referred  to  the  turning  of  the  face  to  one 
side  in  "  insutificiency  of  the  interni"  to  aid  the  weak  adductors, 
but  he  said  nothing  of  the  peculiar  carriage  of  the  head  in  hyper- 
phoria, which  is  equally  common, 

6.  A  peculiar  facial  expression  will  often  be  noticed,  especially 
when  an  hyperphoric  is  in  animated  conversation;  several  furrows 
will  ridge  themselves  above  one  eyebrow,  and  even  the  eyebrow 
itself  may  be  raised  above  the  level  of  its  fellow  from  4  to  10  mm., 
giving  a  quizzical  expression  to  the  face.  There  should  also  be 
mentioned,  in  this  connection,  the  wide  open  eye,  or  stare,  seen 
in  many  hyperphorics.  Occasionally  an  apparent  ptosis  of  many 
years'  duration  is  dispelled  by  prismatic  or  operative  correction  of 
hyperphoria. 


144  FUNCTIONAL   ANOMALIES. 

Not  less  important,  as  immediate  symptoms  of  vertical  deviation 
tendencies,  are  the  painful  eyes,  photophobia  and  drowsiness 
induced  by  any  long-continued  near  work,  notwithstanding  that 
the  patient  is  wearing  proper  lenses. 

The  reflex  symptoms  of  hyperphoria  include  more  or  less  con- 
stant headaches,  amounting  sometimes  to  a  migraine,  nausea, 
vomiting,  dizziness,  and  vertigo.  In  some  instances  the  latter  is 
so  marked  as  to  cause  momentary  unconsciousness  and  a  symptom- 
complex  that  has  more  than  once  led  to  a  diagnosis  of  epilepsy 
or  even  cerebral  tumor.  We  believe  it  is  the  latter  class  of  cases 
that  are  vaunted  by  many  as  instances  of  essential  epilepsy  par- 
tially or  even  entirely  curable  by  eye-treatment  alone. 

The  headaches  of  hyperphorics  are  almost  invariably  aggra- 
vated by  near  work;  also  by  moving  in  a  crowd  or  watching  rapidly- 
moving  objects  (panorama  headache  of  Bennett).  Other 
hyperphorics  will  escape  the  headaches,  but  present,  instead, 
frequently  recurring  nausea,  vomiting  and  vertigo,  the  latter 
especially  brought  on  by  any  continued  looking  up  or  down. 

Etiology. — Intrinsic  hyperphoria  is  commonly  due  to  over- 
action  on  the  part  of  one  muscle  (hyperkinesis)  or  underaction  on 
the  part  of  another  (hypokinesis).  It  may  also  result  from  ano- 
malies in  the  formation  and  relative  position  of  the  orbits  or  from 
peculiarities  in  the  attachment,  development,  insertion  or  action 
of  one  or  more  muscles.  Age  is  now  by  general  consent  admitted 
as  one  of  the  factors  in  the  unveiling  if  not  in  the  production  of 
hyperphoria.  In  a  series  of  cases  reported  by  one  of  us  in  1900, 
one-third  were  under  thirty  years  of  age  and  two-thirds  over  that 
age.  (Compare  with  the  same  facts  in  exophoria).  We  have 
found  intrinsic  hyperphoria  in  a  child  of  twelve,  but  this  is  unusual. 
There  is  no  satisfactory  explanation  for  the  increase  or  perhaps 
unmasking  of  a  latent  hyperphoria.  The '  parallel  process  of 
uncovering  of  latent  hypermetropia  by  advancing  years  naturally 
suggests  itself  and  may  have  much  to  do  with  this  seeming  actual 
increase  in  hyperphoria.  Congenital  paresis  of  one  of  the  ele- 
vators or  depressors — usually  the  superior  recti,  is  a  not  infrequent 
cause  of  hyperphoria  (or  hypo-phorisL)  as  will  be  alluded  to  later  on. 


HYPERPHORIA. 


145 


Diagnosis. — The  assertion  that  hyperphoria  exists  in  a  given 
case  ought  not  to  be  based  on  any  one  test,  but  demands  corrob- 
oration by  every  test  at  our  command.  No  problem  in  ophthal- 
mology calls  for  greater  accuracy  and  adjustment  of  instruments 
and  close  observation.  When  we  say  hyperphoria  we  use  a 
clinically  convenient  term.  We  have  not  told  whether  one  visual 
axis  is  abnormally  high  or  the  other  abnormally  low  nor  have  we 


Fig.  55.^Reimold's  optometer. 

implicated  any  particular  one  of  the  elevators  or  depressors. 
So  that  after  we  have  established  the  diagnosis  of  hyperphoria 
(or  simply  a  deviation  of  one  visual  axis  above  or  below  the  other) 
we  should  endeavor  to  discover  if  possible  whether  one  axis  has  a 
tendency  to  become  abnormally  high  or  the  other  abnormally  low. 
In  conducting  many  of  the  tests,  Risley's,  Reimold's  or  some 
similar  combination  of  the  optometer  and  phorometer  (Fig.  55) 
gives  satisfactory  results. 


146  FUNCTIONAL  ANOMALIES. 

Maddox  Rod  Test. — When  the  patient's  face  has  been  brought 
close  up  against  the  back  surface  of  the  optometer,  and  the  latter 
been  found  to  be  absolutely  level  by  means  of  the  plummet  or 
spirit  level  attached  for  the  purpose,  the  compound  Maddox 
rod  is  slipped  into  one  of  the  cells,  say  the  right  one,  and  so 
turned  that  the  streak  of  light  is  exactly  horizontal.  If  the  streak 
passes  above  the  flame,  there  is  shown  either  right  A^'/Jophoria 
(downward  tendency  of  right  eye),  or  left  hypei"^hor\di  (upward 
tendency  of  left  eye).  If  the  streak  be  found  below  the  flame 
there  is  right  M'^erphoria  (upward  tendency  of  the  right  eye) 
or  left  M'/>ophoria  (downward  tendency  of  the  left  eye).  The 
same  facts  hold  good  when  the  Maddox  rod  is  placed  before  the 
left  eye,  so  that  the  test  can  be  applied  by  placing  the  rod  before 
either  eye.  The  prism  that  carries  the  streak  into  the  flame  is  the 
measure  in  degrees  of  the  hyperphoria. 

Some  prefer  to  use  the  phorometer,  but  the  Maddox  rod  has  an 
added  advantage  in  that  if  the  hyperphoria  appears  to  be  of  a 
different  amount  according  as  the  Maddox  rod  is  placed  before 
one  or  the  other  eye,  we  thus  learn  that  there  must  be  a  slight 
paresis  of  one  of  the  elevators  or  depressors;  that  when  the  paretic 
eye  fixes,  the  separation  of  the  light  and  the  streak  will  be  greater 
(answering  to  the  secondary  deviation)  than  when  the  sound  eye 
fixes.  On  the  other  hand,  in  some  individuals  the  impulse  to  bin- 
ocular vision  is  so  overpowering  a  thing  that  they  will  frequently 
fuse  the  light  and  the  streak,  thus  covering  up  their  muscular 
error;  but  if  the  rod  is  quickly  reversed  several  times  in  the  trial 
frame  from  the  vertical  to  the  horizontal  position  one  is  much 
likelier  to  break  up  the  strong  fusion  impulse  in  such  a  case  and 
get  at  the  true  deviation. 

Diplopia  Tests. — If  the  phorometer  be  used,  the  prism  or 
prisms  with  which  diplopia  is  effected  are  already  in  position, 
and  if  one  image  be  higher  than  the  other,  all  that  remains  to  be 
done  is  to  rotate  the  prisms  by  means  of  the  small  lever  until 
the  images  are  level,  when  the  resultant  right  or  left  hyperphoria 
will  be  indicated  by  the  pointer  on  the  arc  graduated  in  degrees 
on  the  front  of  the  phorometer,  and  can  be  readily  read  off. 


HYPERPHORIA.  I47 

Parallax  Test. — Seal  the  patient  20  feet  or  farther  from  some 
small  object  that  is  situated  directly  in  front  of  and  on  a  level 
with  the  eyes.  The  object  (a  small  luminous  point  of  light  in  the 
middle  of  a  large  black  area,  for  instance)  must  be  so  placed  that  it 
will  not  be  projected  upon  any  surface  back  of  it.  Note  carefully 
that  the  patient's  head  is  not  tilted  to  one  side,  then  carrying  some 
sort  of  cover  to  and  fro  several  times  from  one  eye  to  the  other, 
the  patient  is  requested  to  watch  closely  whether  the  object  as 
seen  by  one  eye  appears  any  higher  than  the  other.  If  so,  vertical 
imbalance  is  present  and  its  degree  is  to  be  determined  by  the 
prism  that  will  make  the  object  appear  on  the  same  level  with 
each  eye.  It  will  sometimes  be  necessary  to  carry  the  cover  from 
one  eye  to  the  other  fifteen  to  twenty  times  before  any  difference 
in  level  in  the  apparent  position  of  the  object  becomes  noticeable, 
but  by  this  means  the  lower  degrees  of  hyperphoria  are  frequently 
unmasked.  The  parallax  test,  when  thoroughly  understood,  is 
susceptible  of  great  delicacy  of  application  and  by  it  1 1 2  degree 
of  hyperphoria  is  easily  detected.  Duane,  whom  we  must  thank 
for  the  test,  claims  that  he  thus  estimates  even  i  /4  degree  of 
hyperphoria. 

If  the  patient  be  ametropic,  he  must  wear  his  correction  during 
all  the  tests.  Thus  far  we  have  determined  only  that  one  ocular 
axis  has  a  tendency  to  deviate  above,  or  the  other  below  the  axis  of 
the  fellow^  eye.  We  have  not  located  the  defect  nor  decided 
whether  it  be  due  to  overaction  of  the  muscles  of  one  eye,  or 
underaction  of  the  corresponding  muscles  of  the  other  eye. 
Resort  must  now  be  had  to  prisms,  to  learn  the  prism  power  of 
upward  and  downward  rotation.  This  will  be  found  to  fluctuate 
from  2  to  3  degrees,  but  the  fact  of  prime  importance  is  that 
whatever  the  power  of  prism  rotation,  supraduction  and  infraduc- 
tion  should  be  equal.  If  the  eyes  can  overcome  a  3  degree  prism, 
base  down,  they  should  likewise  overcome  a  3  degree  prism,  base 
up.  A  difference  of  i  degree  or  more  between  the  supraduction 
and  infraduction  of  the  same  side  indicates  the  probable  existence 
of  hyperphoria;  moreover,  a  supraduction  exceeding  3  degrees 


148  FUNCTIONAL  ANOMALIES. 

(except  in  moderate  and  high  myopia)  is  always  suspicious  and 
presumptive  of  hyperphoria. 

If  there  be  suspicion  of  hyperphoria  and  the  supraduction  and 
infraduction  as  found  by  prisms  prove  equal,  it  becomes  necessary 
to  map  out  the  field  of  monocular  fixation,  especially  the  upward 
and  downward  limits.  This  is  done  by  having  the  patient  follow 
with  the  eye  (but  not  with  the  head)  a  very  small  test-object,  such 
as  a  black  dot  on  a  white  card,  which  is  carried  as  far  up  and  as 
far  down  the  arc  of  the  perimeter  as  the  eye  will  follow  it  without 
wavering  or  receiving  a  blurred  image  of  the  object.  The  arc 
through  which  the  eye  has  rotated  may  be  measured  by  the  peri- 
meter, the  head  resting  on  the  chin-support  and  the  fellow  eye 
excluded  as  in  ordinary  perimetry.  This  examination  should 
show  at  least  35  degrees  to  ^8  degrees  of  upward,  and  from  50  to 
55  degrees  of  downward  rotation.  For  the  precise  measurement 
of  these  rotations,  Stevens  employs  his  tropometer  (described 
above),  and  if  upward  rotation  falls  short  of,  or  exceeds,  32 
degrees,  or  if  downward  rotation  exceeds  or  falls  short  of 
55  degrees,  the  corresponding  elevators  or  depressors  are  to  be 
viewed  as  causative  in  the  hyperphoria.  If  upward  rotation  is 
excessive,  the  hyperphoria  is  likely  due  to  overaction  on  the  part 
of  the  elevators  of  the  hyperphoric  eye.  If  downward  rotation  be 
excessive,  the  hypophoria  is  likewise  due  to  excessive  action  (hy- 
perkinesis)  of  the  depressors  of  the  hypophoric  eye.  If  upward 
or  downward  rotation  be  insufficient  (hypokinesis),  the  deviation 
is  probably  due  to  weakness,  or  even  paresis  of  one  or  more  of 
the  vertical  muscles,  in  which  case  diplopia  can  be  readily  elicited 
when  the  eyes  (but  not  the  head)  are  turned  20  degrees  or  more 
from  the  primary  position,  the  diplopia  increasing  as  the  test- 
object  is  carried  in  the  direction  of  the  weak  muscles. 

Much  information  may  sometimes  be  gained  by  search  of  the 
extreme  upper  periphery  of  the  binocular  fixation  fields  with  a 
one  candle  electric  light  in  a  darkened  room,  a  red  or  cobalt 
glass  placed  before  one  eye,  to  learn  whether  there  is  paresis  of 
any  of  the  elevators  and  similarly  in  the  extreme  lower  field  for 
paresis  of  any  of  the  depressors.     Hyperphoria  and  hypophoria 


HYPERPHORIA.  I49 

may  be  thus  at  times  differentiated.  For  instance:  V.  M.  M., 
female,  married,  twenty-three,  referred  by  her  physician  on 
account  of  panorama  headache,  also  train  and  trolley  nausea 
and  vertigo,  so  marked  that  she  could  not  ride  more  than  eight  to 
ten  blocks  in  the  trolley  cars.  Use  of  her  eyes  for  reading  and 
sewing  was  limited  to  fifteen  to  twenty  minutes,  and  this  in 
spite  of  the  fact  that  she  was  wearing  a  good  correction.  She 
was  a  tall,  thin,  poorly  nourished  girl,  hyperesthetic  and  on  the 
verge  of  neurasthenia.  Both  eyes  were  normal  anteriorly  and 
with  her  correction,  which  was: 


R.  +50+1.00  cyl.  100  degrees 
L.  +75  +  0.90  cyl.    80  degrees 


vision  was  full  and  sharp  5/4  in  each  eye.  The  eye  grounds 
showed  the  irritation  and  low  grade  congestion  so  often  found  with 
such  muscular  anomalies.  Her  muscle  status  was  exophoria  of 
2  degrees  for  infinity  and  5  degrees  for  the  occupation  distance. 
There  was  right  hyperphoria  of  8  degrees  for  infinity  (when  the 
eyes  were  in  the  primary  position)  and  9  degrees  at  the  occupation 
distance.  Search  for  diplopia  in  the  extreme  upper  periphery  of 
the  binocular  fixation  field  revealed  vertical  diplopia  with  the 
left  image  higher  in  the  middle  and  left  upper  field,  most  marked 
in  the  left  upper  field  where  the  separation  of  the  images  was 
about  4  inches.  Paresis  of  the  left  superior  rectus  was  thus 
plainly  shown.  On  questioning  her  I  learned  that  for  years  she 
had  occasionally  seen  double  when  she  looked  at  anything  far  up 
to  the  left,  but  thought  nothing  of  it.  So  that  the  apparent 
diagnosis  of  right  hyperphoria  in  the  case  immediately  gave  way 
to  the  proper  one  of  paretic  left  hypophoria.  It  may  be  stated, 
in  passing,  that  a  4  degree  prism  base  up  was  incorporated  in  her 
left  glass  and  after  two  years  use  of  it  she  can  ride  25  miles  in 
a  trolley  car  without  the  slightest  ocular  disturbance,  she  has  lost 
all  her  headaches  and  hyperesthesia,  and  can  use  her  eyes  for  one 
and  one-half  to  two  hours  at  near  work  comfortably. 

Finally,  when  the  tests  for  hyperphoria  at  20  or  more  feet  are 
concluded,  search  should  be  made  for  vertical  imbalance  at  15  to 


150  FUNCTIONAL  ANOMALIES. 

20  inches.  In  this  test  Graefe's  dot  and  line  may  be  used  or 
the  dot  only.  Better  yet  is  the  small  one  candle  electric  light 
(suggested  for  the  similar  test  in  exophoria)  to  be  held  at  13  to  15 
inches.  Any  vertical  imbalance  will  then  be  recognized  the 
moment  the  Maddox  rod  is  placed  before  either  eye  and  the 
amount  readily  measured.  The  patient  should,  of  course,  wear  the 
proper  correction  (accurately  centered)  during  this  test  and  if 
presbyopic  should  wear  that  correction.  It  will  frequently  be 
found  that  hyperphoria  for  15  inches  is  a  trifle  more  than  for 
distance. 

The  Relation  Between  Hyperphoria  and  Lateral  Deviation 
Tendencies. — It  has  been  claimed  that  many  cases  of  esophoria 
and  exophoria  are  directly  dependent  upon  and  caused  by  a 
tendency  to  upward  deviation  of  one  of  the  visual  axes,  and  no 
doubt  there  is  much  truth  in  this  claim.  It  is  easy  to  conceive  that 
when  vertical  tension  is  out  of  equilibrium  the  lateral  muscles  in 
their  efforts  to  fuse  images  will  tend  to  turn  the  eyes  now  in  and 
now  out,  or  will  acquire  a  habit  of  forcing  the  lateral  tendency  in 
one  or  the  other  direction.  This  dependence  has  been  illustrated 
by  comparing  the  lateral  muscles,  in  their  efforts  to  fix,  with 
the  lifting  of  a  log  with  a  pair  of  tongs,  the  clamps  of  which  are 
not  in  a  horizontal  line.  Many  cases  have  been  reported  where 
not  only  deviation  tendencies,  but  actual  lateral  turnings  have 
been  cured  by  restoration  of  vertical  equilibrium,  and  in  the  con- 
sideration of  causes  which  lead  to  exophoria  or  esophoria,  vertical 
tensions  should  be  given  a  prominent  place.  Theoretically,  all 
cases  of  uncorrected  hyperopia  ought  to  have  upward  and  inward 
tendencies  on  account  of  the  resultant  action  of  all  the  external 
muscles  supplied  by  the  3rd  nerve,  and  the  reverse  will  hold  in 
exophoria,  namely:  a  tendency  down  and  out.  This  interde- 
pendence can  be  well  shown  when  the  grade  of  the  defect  is  high 
enough  to  allow  of  diplopia  with  the  cobalt  glass  test.  It  will 
be  found  by  this  test  that  there  are  few  cases  of  lateral  turnings 
that  are  not  complicated  with  vertical  turnings,  and  it  will  also 
be  found  that  hyperphoria  frequently  changes  from  one  eye  to  the 
other,  according  to  the  eve  used  in  fixation.    If  the  right  eve  should 


HYPERPHORIA.  151 

fix  and  the  left,  armed  with  the  cobalt  glass,  sees  the  false  image 
to  the  left  and  below,  we  have  hyperesophoria  (really  hypereso/ro/>fa 
while  the  cobalt  glass  is  before  the  eye),  and  if  the  glass  is  trans- 
ferred to  the  other  eye,  that  eye  now  sees  the  false  image  and  we 
have  R.  hyperesophoria.  In  other  words,  the  cobalt  glass  deter- 
mines the  fixing,  and  hence,  also,  the  squinting  eye.  The  reason 
for  the  association  of  hyperphoria  with  esophoria  in  hyperopia 
has  already  been  explained,  and  an  analogous  explanation  fits 
the  association  of  hyperphoria  with  exophoria.  If  we  admit  that 
the  tendency  outward  is  a  passive  anomaly  and  due  to  a  loss  of 
converg/snce,  this  deficiency  of  innervation  affects  not  only  lateral 
but  also  vertical  tensions,  and  where  we  should  have  in  esophoria 
hyperphoria,  we  should  expect  to  find  in  exophoria  hypophoria. 
Therefore,  in  considering  the  treatment  of  exophoria  or  esopho- 
ria, the  condition  of  the  vertical  tensions  must  be  thoroughly 
investigated  and  their  causative  relations  determined  where 
possible.  The  question  often  is  raised,  does  the  lateral  imbalance 
depend  upon  the  hyperphoria,  or  is  the  reverse  true  ?  The  answer 
to  this  question  depends  upon  the  relative  rotational  powers  of 
the  vertical  and  lateral  muscles.  If  the  abductors  and  adductors 
show  normal  rotations  (as  determined  by  means  of  prisms  and  the 
tropometer)  the  elevators  or  depressors  are  likely  at  fault.  If  these 
latter  exhibit  normal  and  proportionate  dynamic  conditions,  the 
lateral  muscles  are  probably  causative;  for  instance,  Mr.  L.,  aged 
thirty-one,  a  minister  of  the  gospel  and  a  close  student,  exhibits 
with  the  Maddox  rod  at  20  feet,  exophoria  of  i  degree  and  R.  hy- 
perphoria of  I  degree.  At  20  inches  the  Maddox  rod  showed 
exophoria  12  degrees.  Were  now  the  lateral  or  vertical  muscles 
at  fault  ?  Estimation  of  the  prism  power  of  rotation  with  rotary 
prisms  showed :  Abd.  =  6  degrees;  add.  =  18  degrees;  R.  Supra  ==3 
degrees;  R.  Infra  =1  degree.  The  lateral  muscles  were  there- 
fore proportionate  in  their  tensions  and  the  difference  of  2  degrees 
in  the  right  supra-  and  infraduction  was  sufficient  to  fix  the  vertical 
muscles  as  the  offending  ones;  in  this  particular  case  the  fault 
consisted  in  either  overaction  of  the  elevators  of  the  right  eye 
or  the  depressors  of  the  left  eye — or  underaction  of  the  depres- 


152  FUNCTIONAL  ANOMALIES. 

sors  of  the  right  eye  or  elevators  of  the  left  eye.     This  last  point  of 
overaction  or  underaction  is  to  be  determined  by  the  tropometer. 
Treatment. — The   treatment   of   hyperphoria   resolves   itself 
into  four  phases. 

1.  Exclusion  of  any  general  disease  or  affection  of  the  central 
nervous  system,  incipient  tabes  and  general  paresis  in  particular. 

For  instance:  M.  A.,  aged  thirty-four,  broker,  referred  by  his 
family  physician  on  account  of  eye  symptoms,  showed  4  degrees 
of  left  hyperphoria.  No  diplopia  could  be  shown  in  any  part  of 
the  binocular  fixation  field.  There  was  no  other  abnormality 
about  the  eyes  save  incipient  Argyll-Robertson  pupils,  which  led 
to  the  suggestion  that  he  consult  a  neurologist.  One  year  later 
without  the  use  of  any  correcting  glasses  (as  he  was  practically 
emmetropic)  the  hyperphoria  had  disappeared  entirely,  but  the 
Argyll-Robertson  phenomenon  was  completely  developed,  and 
his  accommodation  was  normal.  Obviously  it  would  have  been 
bad  practice  to  resort  to  either  prisms  or  operation  in  such  a  case. 

2.  Thorough-going  refraction  just  as  in  esophoria  and  exophoria, 
the  correction  being  done  under  cycloplegia  up  to  forty-five  years 
of  age.  The  persistent  use  of  such  corrections  will  suffice  in 
many  cases  if  not  to  partially  or  entirely  dispel  the  hyperphoria,  at 
least  to  render  the  patient  so  comfortable  that  treatment  of  the 
vertical  imbalance  as  such  need  not  be  considered.  We  have 
already  recited  such  a  case  history.  It  must  be  admitted,  however, 
that  correction  of  the  refraction  does  not  of  itself  so  often  prove 
the  only  necessary  factor  as  it  does  in  esophoria  and  exophoria. 
In  our  experience,  esophorics  profit  most  by  a  good  correction 
alone,   exophorics  not   so  often,   and  hyperphorics  least  often. 

3.  If,  after  faithful  use  of  a  good  correction  and  careful  atten- 
tion to  life  habits,  the  hyperphoria  persists  and  is  annoying,  it  is 
well  to  try  the  effect  of  a  prism  or  prisms  that  correct  about 
1/3,  of  the  hyperphoria.  A  convenient  method  is  to  have 
the  prisms  slipped  into  what  is  known  as  an  extra-front, 
to  be  hooked  over  the  regular  glasses  (Fig.  56).  The 
prism  effect  may  be  divided  between  the  two  eyes  {base  doimi 
before  one,  base  up  before  the  other),  or  the  whole  prism  to  be  used 


HYPERPHORIA.  1 53 

may  be  placed  base  down  before  the  hyperphoria  eye,  preferably 
the  former  for  reasons  to  be  stated  later.  By  this  means  prompt  and 
at  times  surprising  relief  is  sometimes  obtained,  as,  for  instance, 
in  the  following  case:  F.  E.,  aged  twenty,  a  goldsmith,  works 
all  day  at  a  distance  of  from  8  to  lo  inches  soldering  small  gold 
trinkets.  Given  eighteen  months  ago  by  a  colleague  (who  used  a 
cycloplegic)  R.  E.  +  .50  D+.50  Cyl  90  degrees  L.  E.  +  0.75  ^^'^• 
With  this  correction  he  was  much  more  comfortable  at  his  work  for 
two  or  three  months,  but  his  eyes  and  head  began  to  trouble  again, 
when  his  oculist,  after  much  pains,  ordered  a  i  /2  degree  prism, 


Fig.  56. — Hook  or  extra  front. 

base  down,  to  be  incorporated  in  the  left  glass,  indicating  that  he 
found  left  hyperphoria.  (This  point  is  emphasized  because  of  the 
subsequent  developments  in  the  case).  Again  he  pursued  his 
work  with  renewed  comfort  for  about  three  months,  when  the 
old  train  of  eye  and  head  symptoms  once  more  took  up  its  march. 
At  this  time  he  came  under  our  observation,  and  on  September 
14,  1897,  he  was  carefully  refracted  under  thorough  cycloplegia 
and  the  findings  of  the  previous  worker  were  confirmed  in  all 
but  the  muscular  details. 

September  16,  1897.  Maddox  rod  shows  esophoria  i  /2  degree. 
No  hyperphoria.  Abduction  =7  degrees.  Adduction  =15 
degrees.     Left  supra-  and  infraduction  =  3  degrees. 

September  30,  1897.  Maddox  rod  used  over  patient's  correc- 
tion shows  exophoria  i  degree.  Right  hyperphoria  i  /2  degree. 
{Left  hyperphoria  had  been  found  by  his  former  adviser).  With 
the  parallax  test  R.  hyperphoria  i  1/2  degrees.  Exophoria 
2  degrees. 

October  14,  1897.     Left  hyperphoria  i  degree  full,  with  parallax 


154  FUNCTIONAL   ANOMALIES. 

test.  Maddox  rod  shows  vertical  balance.  Control  tests  made 
four  times  during  the  succeeding  month  showed  R.  hyper- 
phoria I  degree  full  with  the  parallax  test,  and  each  time  R. 
supraduction  equalled  41/2  degrees,  while  R.  infraduction 
equalled  21/2  degrees. 

This  accord  in  results  in  four  consecutive  examinations  justified 
having  the  i  /2  degree  prism,  base  down,  taken  out  of  the  correction 
of  his  left  eye  and  having  him  try  a  3  /4  degree  prism,  base  down, 
before  the  right  eye  in  a  slip  front  to  be  hooked  on  over  his 
glasses  while  at  work.  One  month  later  he  stated  that  he  had 
never  been  so  comfortable.  He  was  then  directed  to  have  the 
3/4  degree  prism,  base  down,  incorporated  into  his  right  glass, 
because  he  was  so  much  annoyed  by  the  reflections  from  the 
prism  in  the  extra  front.  Four  months  later  the  patient  stated  that 
he  was  working  at  his  soldering  bench  (at  a  distance  of  8  inches) 
for  10  hours  a  day,  without  discomfort  of  eyes  or  head. 

This  case  illustrates  how  the  most  careful  worker  may  be  led 
into  error  by  a  spastic  hyperphoria  which  we  believe  this  young 
man  to  have  shown  in  the  earlier  part  of  his  trouble.  Later, 
long-continued  observation  of  his  case  and  prism  estimation  of  the 
upward  and  downward  rotation  showed  not  only  right  hyper- 
phoria, but  the  difference  between  the  right  supraduction  (4  i  /2 
degrees)  and  infraduction  (2  i  J2  degrees)  pointed  to  the  overact- 
ing elevators  of  the  right  eye.  as  the  cause  of  the  deviation.  Theo- 
retically, tenotomy  of  the  right  superior  rectus  or  of  the  corre- 
sponding inferior  oblique  was  indicated,  but  prisms  in  the  position 
of  rest  (favoring  the  underacting  or  weaker  depressors  of  the 
right  eye)  gave  the  patient  such  prompt  and  lasting  relief  that 
operative  measures  were  not  to  be  thought  of. 

Naturally  there  are  those  who  contend  that  the  prism  is  but  a 
crutch  that  must  needs  be  added  to  from  time  to  time  to  the  great 
disadvantage  of  the  patient's  ocular  muscles,  but  as  there  is  almost 
no  other  alternative  but  operation,  prisms  must  be  considered  and 
must  be  offered  to  the  patient  as  a  possible  means  of  relief.  Also 
there  are  those  who  claim  that  if  in  a  given  case  2  degrees  of 
hyperphoria  are  definitely  shown,  that  a  2  degree  prism  should  be 


HYPERPHORIA.  1 55 

incorporated  in  the  patient's  lenses  to  establish  vertical  balance 
once  and  for  all.  From  the  academic  standpoint  this  would  seem* 
to  be  perfectly  reasonable,  but  abundant  experience  has  shown 
that  the  average  patient  glides  much  more  easily  into  the  com- 
fortable use  of  vertical  prisms  if  one-third  to  one-half  of  the  devia- 
tion for  distance  is  employed,  having  the  patient  to  understand 
that  as  time  goes  on  more  prism  strength  may  be  demanded  by 
the  eyes. 

Latent  hyperphoria  is  ofttimes  uncovered  by  the  latter  process 
and  there  is  every  reason  to  believe  that  once  a  patient's  full 
hyperphoria  has  been  learned  by  this  method  there  is  little  likeli- 
hood that  any  more  deviation  will  reveal  itself  no  matter  how 
long  the  case  is  studied.  We  have  a  long  series  of  cases  in  support 
of  this  belief.  Yet  warmly  as  we  wish  to  endorse  the  practice 
of  temporary  trial  of  prisms  in  the  hook  front,  there  are  many 
individuals  whose  symptoms  are  only  aggravated  by  this  measure, 
in  which  case  exercise  of  the  vertical  muscles  may  be  tried -by 
means  of  prisms  placed  base  up  or  down,  as  the  case  requires. 
Savage  believes  this  method  to  be  of  value  in  deviation  ten- 
dencies under  i  1/2  degrees,  and  says:  "The  prisms  used 
should  range  from  1/4  to  2  degrees;  most  cases  will  not  require 
stronger  than  a  i  degree  prism.  The  apex  of  the  prism 
should  be  placed  in  the  direction  of  action  of  the  muscles 
to  be  developed,  the  patient  exercising  from  two  to  ten  minutes, 
two  to  five  times  daily.  The  object  looked  at  must  be  20  feet 
distant,  and  it  should  be  seen  through  the  prism  5  seconds,  and 
then  without  the  prism  5  seconds,  and  so  on  throughout  the  sitting." 
While  our  own  experience  with  this  method  in  hyperphoria  has 
been  limited,  our  results  have  not  been  such  as  to  lead  us  to 
expect  much  relief  from  this  kind  of  training. 

If,  then,  a  patient  presents  persistent  hyperphoria  and  will 
tolerate  neither  prisms  in  position  of  rest  nor  exercise  of  the  weaker 
muscles,  are  we  to  turn  immediately  to  operation  as  a  last  resort  ? 
Not  so.  Many  factors  must  be  determined  before  operative 
treatment  is  applicable.  For  instance,  it  is  not  to  be  thought  of 
when  the  hyperphoria  is  recent,  progressive,  or  variable;  in  case  of 


156  FUNCTIONAL   ANOMALIES. 

central  nervous  disease,  in  rheumatic,  gouty  or  diabetic  subjects, 
or  in  those  who  have  not  enjoyed  binocular  vision  for  years 
(strictly  speaking,  these  are  instances  of  hyperlropia).  Moreover, 
when  hyperphoria  complicates  esophoria  or  exophoria,  it  is  not 
infrequent  for  the  vertical  anomalies  to  right  themselves,  or  at 
any  rate  for  the  symptoms  attributed  to  them  to  disappear  when 
the  lateral  muscles  have  been  well  trained  with  prism  gymnastics. 
Particularly  is  this  true  when  exophoria  coexists. 

4.  Operation. — Hence  we  find  operative  treatment  of  the  hyper- 
phorias narrowed  down  to  the  permanent,  constant  or  static 
variety,  where  the  deviation  tendency  is  constant  in  amount  and 
character  notwithstanding  at  least  six  months  of  the  proper  cor- 
rection, where  all  tests  agree  in  showing  marked  over  or  under- 
action of  one  set  of  elevators  or  depressors,  when  prisms  have 
not  been  well  borne,  and  exercises  are  of  no  avail. 

In  the  former  set  of  cases  (overaction)  tenotomy  is  highly 
satisfactory  and  often  brilliant  in  results,  if  the  case  has  been 
selected  in  accordance  with  the  above  suggestions.  The  dis- 
sipation of  reflex  symptoms  following  upon  tenotomy  for  hyper- 
phoria is  sometimes  little  short  of  wonderful,  and  has  doubtless  led 
many  witnesses  of  such  cures  into  operative  treatment  of  hyper- 
phorias that  are  distinctly  outside  of  the  operative  class,  and 
given  the  extreme  illogical  conservatives  in  ophthalmology  occa- 
sion to  deride  the  judicial  and  unjudicial  alike  as  "muscle- 
snippers." 

Hyperphoria,  constant  in  degree  and  kind,  definitely  due  to 
underaction  on  the  part  of  the  vertical  muscles,  may  be  met  by 
advancement  or  muscle  shortening  of  the  underacting  muscle  or 
muscles,  and  in  properly  selected  cases  the  same  results  may,  as  a 
rule,  be  expected.  It  should  be  borne  in  mind,  however,  that  ad- 
vancement of  a  vertical  muscle  is  not  so  easily  performed  as  on  a 
lateral  one  and  this  may  influence  the  surgeon  to  resort  to  tenotomy 
of  the  opposing  muscle. 

Operation,  whether  tenotomy  or  advancement,  should  always 
aim  to  slightly  under-correct  the  deviation,  the  remainder  being 
often  amenable  to  prism  exercise  of  the  weak  muscle  immediately 


DECENTERING    LENSES.  1 57 

and  from  twenty-four  to  forty-eight  hours  after  the  operation; 
in  this  way  the  effect  of  an  operation  that  is  insufficient  may  be 
considerably  increased;  any  slight  remaining  deviation  can  be 
readily  met  by  the  necessary  prism  in  the  position  of  rest. 

Surgeons  of  large  operative  experience  with  muscular  ano- 
malies prefer  to  aim  at  a  slight  over-correction  of  the  imbalance, 
because,  as  they  assert,  reattachment  of  the  operated  muscle  is 
almost  sure  to  be  attended  with  some  loss  of  the  original  effect. 
The  practice  is  a  safe  one,  however,  only  in  the  hands  of  those 
who  have  perfected  themselves  in  the  technique  of  operations  on 
the  ocular  muscles. 

DECENTERING  LENSES. 

Some  oculists  prefer  to  decenter  spherocylindrical  lenses  rather 
than  to  write  for  the  lens  and  the  prism  separately.  Especially 
in  Great  Britain  is  this  in  vogue.  If  this  practice  is  to  be  followed 
it  is  well  to  bear  in  mind  the  general  rule  that  for  every  centi- 
meter (or  ID  mm.)  of  decentering  there  will  result  as  many  prism 
degrees  as  there  are  diopters  in  correcting  lens.     Thus: 

+  4.00  sphere  3  4  degree  prism  base  out  may  also  be  written 
4-4.00  sphere  decentered  i  cm.  outward,  (or  10  mm.). 
or     -|-  4.00  sphere  3  2  degree  prism  base  out  may  also  be  written 
+  4.00  sphere  decentered  5  mm.  outward. 

While  the  ophthalmologist  may  occasionally  have  recourse  to 
this  method  of  securing  a  prismatic  effect  we  do  not  recommend  it 
as  a  routine  measure.  Opticians  in  this  country  are  in  the 
habit  of  receiving  prescriptions  as  follows; 

-f-  2.00  sphere -|-  3  ^-S^  cy'-  ^^i^  45  degrees  3  ^  degree  prism 
base  in. 

and  they  then  decenter  the  lens  to  produce  the  proper  effect. 
The  table  prepared  by  Dr.  Edward  Jackson  here  shown  indicates 
the  amount  or  decentering  of  a  lens  of  known  focal  length  to 
produce  a  given  prismatic  effect. 


158 


FUNCTIONAL  ANOMALIES. 


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TESTING    PRISMATIC    LENSES. 


'59 


On  Testing  Prismatic  Lenses. 

The  prescriber  should  be  prepared  to  test  the  correctness  of 
prismatic  lenses  when  they  are  returned  to  him  for  inspection. 

A  common  usage  is  to  select  some  object  in  the  room  with  a 
long  straight  side  to  it  such  as  the  door  jamb.  With  the  sphero- 
cylindrical clement  of  the  lens  properly  neutralized  the  optical 
center  of  the  whole  combination  is  held  before  the  observer's 
right  eye  and  in  line  with  the  door  jamb,  when  that  portion  of  the 


Fig.  57. — Effect  of  a  prism  in  breaking  the  edge  of  a  door  jamb 
or  any  straight  line. 


edge  of  the  jamb  seen  through  the  lens  will  appear  displaced  to 
one  side.  (Fig.  57).  The  prism  that  will  restore  the  displaced 
portion  of  the  door  jamb  so  that  it  appears  continuous  will  be 
the  measure  of  the  prism  that  is  incorporated  in  the  lens. 

This  same  principle  has  been  utilized  by  Zeigler  in  designing 
his  card  for  measuring  the  prism  strength  of  such  lenses.  After 
the  spherocylindrical  portion  of  the  lens  has  been  properly  neutral- 
ized as  in  the  preceding  experiment,  it  is  held  at  one  or  two 
meters  from  the  card  (depending  on  which  distance  the  card  is 


i6o 


FUNCTIONAL  ANOMALIES. 


adapted  for)  and  the  prism  strength  immediately  read  off  accord- 
ing to  the  amount  of  displacement  produced.  It  is  convenient, 
accurate  and  serviceable  (Fig.  58). 

One  other  method  remains,  the  use  of  the  douziememeter.^ 
The  instrument  is  applied  to  first  the  nasal  and  then  the  tem- 
poral edge  of  the  lens,  both  of  which  should  measure  the  same 


16     U     12     10      8      6      4      2 


15 


13 


11 


9 


7 


5 


3 


Fig.  58. — Ziegler's  prism  measure  card. 

in  case  there  is  no  prism  element  in  the  glass  (Fig.  59).  The 
same  is  true  of  the  upper  and  lower  edges  of  the  lens.  If  the 
douziemeter  registers  say  10  douziemes  for  the  nasal  edge  of  a 
lens,  and  6  douziemes  for  the  temporal  edge,  the  nasal  edge  being 
4  douziemes  thicker  represents  a  i  degree  prism  base  in.  A  lens 
that  is  2  douziemes  thicker  at  the  nasal  than  at  the  temporal 
edge  would  represent  a  1/2  degree  prism  base  in  and  a  lens  8 


*  The  name  is  derived  from  tiie  French  douzieme — or  one-twelfth — having  refer- 
ence to  the  old  system  of  twelve  lines  to  the  inch.  The  scale  of  the  douziemeter  is 
marked  in  twelfths  of  an  inch,  or  lines. 


TESTING    PRISMATIC    LENSES. 


l6l 


douziemes  thicker  at  the  nasal  than  at  the  temporal  edge  would 
represent  a  2  degree  prism  base  in.  The  same  method  of 
measurement  holds  in  measuring  the  upper  and  lower  edges  to 
detect  any  vertical  prism  that  may  be  present  in  a  lens. 


Fig.  59. — The  douziemeter. 


HETEROTROPIA, 


ESOTROPIA.^ 


Esotropia  manifests  itself  externally  by  an  inward  deviation  of 
one  cornea,  or  the  inclination  of  the  visual  axes  toward  each 
other,  so  that  they  cross  at  some  point  inside  of  infinity;  or  more 
correctly  speaking,  the  visual  axis  of  one  eye  is  directed  toward 
that  of  the  other." 

Etiology. — The  factors  that  individually  or  in  combination 
produce:  esotropia  are : 

(a)  Refractive  errors  (generally  H  and  Ah  conditions). 

(b)  A  congenitally  weak  fusion-faculty. 

(c)  Congenital  paresis  of  one  or  both  external  recti  (to  be  dis- 
tinguished from  true  congenital  abducens  palsy). 

(d)  Obstetric  injuries  to  the  eyes. 

Refractive  Errors. — The  usual  refractive  status  in  most  subjects 
of  esotropia  is  that  of  compound  hypermetropic  astigmatism. 
The  error  need  not  necessarily  be  high.  Many  esotropic  chil- 
dren do  not  manifest  more  than  2  diopters  of  error.  In  the  cases 
that  are  solely  due  to  the  refractive  error  the  correction  of  the 
abnormal  refractive  status  with  suitable  glasses  generally  causes  the 
strabismus  to  rapidly  disappear.  This  variety  conforms  absolutely 
to  Bonder's  theory  as  to  the  dependence  of  the  deviation  on  the  ab- 
normal convergence  stimulus  set  up  by  the  refractive  error,  and 
may  properly  be  called  accommodative  esotropia.  Not  all  cases  of 
esotropia,  however,  are  explainable  on  this  basis.  Ninety-six 
per  cent,  of  all  children  are  born  hypermetropic  and  the  question 
may  justifiably  be  put,  "  Why  do  not  all  hypermetropic  children 
show  esotropia?"  Some  other  factor  must,  therefore,  be  opera- 
tive and  the  most  probable  one  is  a  Congenitally  Weak  Fusion 
Faculty. 

^  Synonyms. — Internal  or  convergent  strabismus;  internal  squint. 

2  The  student  is  urged  to  read  the  chapters  on  "The  Evolution  of  Binocular 
Vision"  and  "The  Relation  between  Accommodation  and  Convergence"  before 
entering  upon  the  study  of  esotropia. 

165 


l66  FUNCTIONAL  ANOMALIES. 

There  seems  to  be  much  basis  for  the  supposition  that  certain 
children  exhibit  a  very  weak  fusion  faculty. 

Whether  this  is  due  to  hereditary  influence  or  to  imperfect  devel- 
opment of  the  entire  visual  apparatus  during  foetal  life  is  still  a 
mooted  question.  Nevertheless,  the  fact  remains  that  a  goodly 
percentage  of  esotropic  children  are  the  subjects  of  this  weakness, 
in  consequence  of  which  the  child's  eyes  do  not  acquire  normal 
conditions  and  sooner  or  later  begin  to  exhibit  abnormal  devia- 
tion (generally  in  the  direction  of  convergence).  It  will  be 
readily  seen,  therefore,  that  in  this  variety  of  cases  it  matters  little 
whether  the  refractive  condition  is  hypermetropic,  emmetropic, 
or  myopic,  the  deviation  develops  quite  the  same;  as  for  instance 
in  the  following  case: 

H.  G.,  aged  three,  brought  because  of  an  esotropia  that  had 
begun  to  appear  about  a  year  previously.  The  little  patient  was  a 
fine,  lusty,  healthy  boy,  whose  personal  and  family  history  were 
good  and  whose  eyes  seemed  to  be  normal  in  every  respect  save 
for  the  deviation,  which  equalled  40  degrees.  Under  thorough 
atropinization  the  eye -grounds  were  found  normal,  and  the  retino- 
scope  showed  only  one-half  a  diopter  of  hypermetropia  without  any 
astigmatism.  In  the  presence  of  so  insignificant  a  refractive  error 
some  other  factor  had  to  be  sought  for  and  it  was  found  that  his 
fusion  faculty  was  practically  absent.  Obviously  the  treatment 
had  to  be  carried  out  without  the  help  of  any  correcting  glasses. 

Or  esotropia  may  be  found  in  a  child  with  myopia,  as  follows : 

W.  S.,  aged  four,  a  strong,  healthy  child  began  to  show  occa- 
sional deviation  of  either  eye  near  the  end  of  his  second  year. 
There  was  no  illness,  no  trauma;  in  fact,  no  contributing  factor  of 
any  kind  that  could  be  made  out.  He  had  three  sisters,  all  of 
whom  presented  normal  eyes.  His  deviation  amounted  to  30 
degrees  in  spite  of  the  fact  that  the  temporal  rotation  of  each 
eye  seemed  normal.  Under  thorough  cycloplegia  the  eye-grounds 
were  found  normal  and  the  retinoscope  established  his  refractive 
status  as 

R.  — i.oo  sph.  — 75  cyl.axis  45  degrees 
L.  — 0.75  sph. — 50  cyl.axis  180  degrees. 


ESOTROPIA.  '  167 

With  his  correcting  glasses  10  degrees  of  the  deviation  disappeared, 
leaving  20  degrees  in  evidence  and  it  so  remained  at  the  end  of  a 
year.  Since  that  time  some  education  of  the  fusion  faculty  has 
been  accomplished  and  today  (after  five  years)  the  deviation 
equals  10  to  12  degrees.  He  now  has  a  fair  chance  to  reach 
manhood  with  an  approximately  straight  pair  of  eyes  and  with- 
out having  been  subjected  to  operation. 

Necessarily  such  cases  are  rare.  The  usual  condition  is  that 
of  a  somewhat  subnormal  fusion  faculty  that  is  embarrassed  in 
its  evolution  by  an  unequal  compound  hypermetropic  astig- 
matism. Indeed,  it  is  our  feeling  that  this  is  the  usual  complex 
in  the  vast  majority  of  cases  presenting  themselves  either  in 
private  or  clinical  practice. 

Congenital  Paresis  of  One  or  Both  External  Recti. — As  stated  in 
the  classification,  this  is  to  be  distinguished  from  true  congenital 
abducens  palsy.  It  is  not  frequently  encountered,  but  one  should 
nevertheless  be  on  his  guard.     For  instance : 

Miss  H.  C,  aged  twenty-six,  comes  for  advice  as  to  her  eso- 
tropia, which  had  shown  itself  mainly  from  her  fourth  year  onward. 
At  her  sixth  year  she  was  refracted  and  for  twenty  years  she  had 
worn  glasses  that  so  lessened  the  esotropia  as  to  entirely  satisfy 
her  as  to  her  appearance.  She  showed  15  to  20  degrees  of 
esotropia,  varying  from  time  to  time.  Her  refractive  status 
was  typically  H  and  Ah,  for  which  she  was  wearing  a  good  cor- 
rection. She  preferred  to  fix  wdth  her  right  eye,  although  the 
vision  was  normal  in  both  eyes.  With  the  tropometer  it  was 
found  that  her  temporal  rotation  in  either  eye  was  but  20  degrees 
(as  against  the  normal  50).  Homonymous  diplopia  was  found 
in  the  extreme  temporal  periphery  of  both  motor  fields,  although 
it  was  not  noted  until  the  light  was  30  to  35  degrees  from  the  median 
line.  It  would  have  been  an  easy  matter  to  overlook  the  some- 
what defective  temporal  rotations  in  these  eyes.  Muscular 
advancement  of  both  external  recti  in  this  case  entu-ely  corrected 
the  defect. 

Obstetric  Injuries  to  the  Eyes. — Within  recent  years  Wolff  and 
von  Sicherer  have  studied  the  eye-grounds  of  newborn  children 


1 68  FUNCTIONAL  ANOMALIES. 

and  have  found  numerous  instances  of  retinal  hemorrhages  not 
only  in  children  who  were  instrumentally  delivered,  but  also  in 
those  who  were  born  without  the  use  of  instruments.  These 
facts  may  have  much  bearing  on  the  genesis  of  esotropia.  If  a 
child  should  be  born  with  an  extensive  retinal  hemorrhage  in- 
volving the  macular  region  and  this  hemorrhage  were  imper- 
fectly absorbed  it  is  not  difficult  to  conceive  that  there  might  be 
sufficient  hindrance  to  the  normal  evolution  of  binocular  vision 
to  induce  suppression  of  the  images  from  that  eye  such  as  occurs 
in  children  with  a  defective  fusion  faculty,  in  which  event  the 


Fig.  6o. — Crossing  of  visual  axes. 

eye  so  affected  might  eventually  deviate  from  parallelism.  If  the 
child  had  a  congenitally  strong  fusion  faculty  the  eyes  would  be 
held  parallel,  but  the  child  would  grow  up  with  a  congenital  ambly- 
opia. It  is  probable  that  this  is  the  explanation  of  that  class  of  cases 
that  come  to  report  from  time  to  time,  of  amblyopic  eyes  seem- 
ingly without  any  ophthalmoscopic  change  and  yet  revealing  a 
well  marked  central  scotoma. 

It  must  be  borne  in  mind  always  that  the  image  of  the  object 
engaging  the  attention  of  the  patient  falls  upon  the  fovea  of  the 
fixing  eye,  and  upon  some  portion  of  the  retina  to  the  nasal  side  of 
the  fovea  of  the  squinting  or  deviating  eye.  Hence,  the  visual 
axes  are  not,  strictly  speaking,  inclined  toward  each  other; 
but  the  axis  of  the  fixing  eye  is  directed  straight  at  the  object, 
while  that  of  the  deviating  eye  intersects  that  of  the  fixing  eye  at 
a  point  nearer  the  face  than  the  object;  in  other  words,  both  eyes 
are  not  abnormally  converged  at  the  same  moment  (see  Fig.  60). 


ESOTROPIA.  169 

The  burden  of  the  convergence  is  borne  by  one  eye  only,  trans- 
ferable under  some  conditions  to  the  other,  but  never  mani- 
fested simultaneously  in  both.  This  statement  is  true  only 
of  the  properly  so-called  functional  esotropias,  and  excludes 
paralysis  of  the  external  muscles  and  association  paralysis. 
Esotropia  is  mmiocular  (or  constant),  and  binocular  (or  alter- 
nating). In  the  former,  one  and  always  the  same  eye,  under  all 
circumstances  is  used  for  fixation,  while  the  former  eye  deviates. 
In  the  latter,  either  eye  is  used  indifferently  for  fixing,  and  the 
squint  is  instantaneously   transferred  to  the   eye  not  so  used. 


Monocular  Esotropia. 


Monocular  esotropia  is  characterized  by  (i)  lowered  vision  or 
even  amblyopia  of  the  squinting  eye;  and  (2)  invariable  fixation 
of  the  other  eye. 

Diagnosis. — The  methods  that  take  into  consideration  the 
apparent  deviations  of  the  visual  axes  are  at  times  misleading. 

For  example,  the  angle  alpha  made 
by  the  intersection  of  the  optic  with 
the  visual  axis  may  be  abnormally 
^^L^^  small,  giving  the  appearance  of  in- 

■BWBL  ternal  strabismus,  while  the  muscles 

43   ^  J  may   be    in    equilibrium.     Too,    the 

interpupillary  distance,  the  shape  of 
the  orbit,  the  size  of  the  commissure 
and  other  anatomic  peculiarities 
should  always  be  taken  into  consid- 
eration. 

The  three  facts  that  should  be  de- 
termined in  every  case  of  esotropia 
are  the  vision,  the  degree  of  deviation, 
and  the  refractive  status. 

Vision. — In  children  under  three 
years  of  age,  estimate  of  the  vision  is 
most  unsatisfactory  and  generally 
impossible.  Between  the  third  and 
the  seventh  year,  some  form  of  object 
test  card  will  be  necessary.  Fig.  61. 
The  one  illustrated  we  have  found  of  great  service.  Naturally 
much  tact  is  required  in  handling  these  little  people,  but  judg- 
ment and  patience  will  be  amply  repaid  when  the  cooperation  of 
the  child  is  secured;  this  once  accomplished  all  the  rest  is  easy. 
In  esotropic  children  under  six  years  of  age,  the  vision  in  the 

170 


Fig.  61. — Reber's  object  or  kin 
dergarten  test  card. 


MONOCULAR    ESOTROPIA.  17I 

deviating  eye  will  seldom  be  found  less  than  5/30.  After  the 
seventh  year  and  on  up  to  puberty  it  frequently  falls  to  5/60  and 
at  times  to  2/60  or  3/60. 

Amblyopia. — No  term  in  all  ophthalmic  literature  has  been 
more  loosely  used  than  this  term  amblyopia.  While  it  admittedly 
means  "indififerent  vision,"  few  writers  seem  to  have  stated  just 
what  degree  of  loss  of  vision  shall  justify  our  use  of  the  term 
amblyopia.  Inasmuch  as  vision  of  at  least  1/4  (5/20  or  20/80) 
is  essential  to  permit  comfortable  use  of  an  eye  for  reading,  it 
would  seem  justifiable  to  fix  that  as  the  arbitrary  mark.  Vision 
of  less  than  5/20  or  20/80  could  be  definitely  set  down  as  ambly- 
opia and  more  than  that  as  not  amblyopic.  It  is  understood  that 
the  ophthalmoscope  shows  no  opacities  in  the  media,  and  that 
the  details  of  the  eye-ground  conform  in  every  particular  to  the 
normal  standard,  although  the  field  of  vision,  as  above  stated, 
is  sometimes  defective,  especially  in  its  central  portion. 

That  no  minute  anatomic  changes  of  the  optic  nerve  occur  in 
the  fovea  or  in  the  foveal  fibers  seems  clear  from  the  report  of 
several  cases  in  which  an  amblyopic  squinting  eye  was  restored 
to  useful  vision  in  the  course  of  a  few  weeks  by  its  enforced  use. 
Again,  the  error  of  refraction  of  the  amblyopic  eye  not  infrequently 
differs  very  little  from  that  of  the  seeing  eye,  certainly  not  enough 
to  account  for  that  grade  of  defect  which  will  exclude  it  from  all 
participation  in  vision.  It  is  probable  that  in  consequence  of  a 
functional  (but  not  anatomic)  defect  in  the  basal  ganglia  or  the 
cortical  centers  for  vision,  acting  in  conjunction  with  a  degree  of 
hypermetropia  high  enough  to  disrupt  the  association  of  con- 
vergence and  accommodation,  one  eye  has  been  excluded  from 
vision  and  its  function  held  in  abeyance.  Whatever  the  ex- 
planation may  be,  it  is  true  that  amblyopia  is  invariably  associated 
with  monocular  squint,  that  it  limits  the  squint  to  one  eye,  and 
stands  in  the  way  of  a  scientific  correction  of  the  muscular  error, 
since  binocular  vision  is  practically  unattainable. 

In  some  cases  restoration  to  parallelism  of  the  visual  axes  can, 
in  fact,  be  effected,  only  for  a  brief  period  however,  since  the 
blurred  image  seen  by  the  amblyopic  eye  interferes  with  the  clear 


172  FUNCTIONAL   ANOMALIES. 

one  seen  by  the  good  eye,  and  in  the  interest  of  good  vision  the  in- 
distinct image  comes  to  be  disregarded  and  an  internal  or  external 
deviation  is  developed.  Improvement  has  been  reported  as  the 
result  of  exclusion  of  the  good  eye,  enforcing  education  and  training 
by  constant  use  of  the  other;  it  has  also  been  claimed  as  a  result  of 
operation,  but  in  our  experience  the  means  often  successfully 
employed  to  correct  squint  in  childhood  without  operation,  such 
as  atropin,  bandaging  of  the  good  eye,  etc.,  have  proved  indifferent 
in  curing  amblyopia,  and  the  hope  that  vision  may  be  restored  to 
a  practical  and  useful  extent  by  these  means  has  not  been 
entirely  fulfilled.  Amblyopia  does  not  signify  blindness  (for 
which  the  obsolete  word  is  amaurosis),  and  when  not  qualified 
by  an  adjective,  such  as  toxic,  renal,  etc.,  indicates  simply  that 
the  patient's  vision  is  defective  from  no  known  causes.  The  use 
of  the  word  should  be  limited  to  those  eyes  whose  vision  is  lower 
than  20/80.  Perseverance  scientifically  applied  will  often  be  re- 
warded by  a  decided  improvement  of  vision  by  correcting  lenses.^ 

Measurement  of  the  Deviation. 

The  means  employed  for  the  measurement  of  the  deviation  are: 
a.  inspection,  b.  the  cover  test,  c.  linear  measure,  d.  the  perimeter 
or  arc  measurement,  e.  the  tape  measurement  or  tangent  measure- 
ment, f.  the  diplopia  test,  g.  the  tropometer  or  rotational  test. 

a.  Inspection. — Inspection  will  show  a  want  of  coordination  of 
the  visual  axes  by  the  fact  that  the  sclera  of  the  temporal  side  of 
the  deviating  eye  is  exposed  in  greater  extent  than  that  on  the 
nasal  side;  furthermore,  that  the  cornea  is  deflected  toward 
the  nose. 

b.  Cover  Test. — The  patient  fixes  the  gaze  on  some  object  20  or 
more  feet  distant.  The  cover  or  screen  is  then  placed  over  the 
fixing  eye  compelling  the  previously  deviating  eye  to  fix,  when  it 
will  be  seen  to  move  from  2  to  5  mm.  to  reach  the  proper  position 

'  Should  the  reader  desire  to  pursue  the  theories  of  amblyopia  farther  than  they  are 
here  discussed,  he  is  referred  to  the  papers  of  Hansen  Grut,  Schweigger,  Schmeich- 
ler,  Priestley  Smith,  Parinaud,  Javal,  Worth  and  others. 


MONOCULAR   ESOTROPIA.  1 73 

for  fixation.  The  degree  of  deviation  can  be  estimated  with  fair 
accuracy  by  interposing  prisms  with  their  bases  out,  increasing 
in  strength  until  all  movement  of  cither  eye  (as  the  screen  is 
carried  to  and  fro  in  front  of  the  eyes)  is  abolished.  The  prism 
strength  required  to  stop  the  movement  of  either  eye  is  the 
measurement  of  the  deviation. 

c. Linear  Measure. — Years  ago  von  Grsefe  devised  a  small  curved 
ivory  scale  marked  in  millimeters  to  be  laid  against  the  lower  lid 
and  the  deviation  then  read  oflf  in  millimeters  (Fig.  62),  but,  as 
Landolt  insists,  it  is  not  exactly  scientific  to  speak  of  an  angular 


Fig.  62. — Graefe's  strabismometer. 

deviation  in  Hnear  terms.  This  may  be  obviated  by  utilizing 
the  images  formed  by  the  corneas  when  a  strong  light  is  thrown 
on  them.  With  the  light  directly  over  the  patient's  head,  a  re- 
tinoscopic  mirror  will  produce  quite  a  bright  corneal  image  if 
thrown  upon  the  eyes  from  one  meter's  distance.  Hirschberg 
estimated  that  this  reflection  image,  if  seen  at  the  corneal  limbus 
represented  a  deviation  of  about  45  degrees;  if  on  the  sclera  it  is 
60  to  80  degrees;  if  midway  between  the  limbus  and  the  margin 
of  an  average  sized  pupil  it  is  about  15  to  20  degrees,  and  if  at  the 
outer  edge  of  the  pupil  about  10  degrees.  With  practice  a  fairly 
accurate  estimate  may  be  made. 

d.  The  Perimeter  or  Arc  Measurement. — The  patient  is  seated 
at  the  perimeter  just  as  for  ordinary  perimetry  only  that  both  eyes 
are  kept  open.  The  non-squinting  eye  is  then  fixed  upon  some 
object  at  infinity  directly  in  line  with  the  center  of  the  perimeter 
arc  while  the  observer  moves  a  small  electric  light  along  the  arc 
of  the  perimeter.  The  image  formed  by  this  light  on  the  cornea 
of  the  deviating  eye  is  studied  and  the  light  moved  backward  and 


174  FUNCTIONAL  ANOMALIES. 

forward  along  the  arm  of  the  perimeter  (which  should  be  in  the 
horizontal  meridian)  until  the  tiny  corneal  image  rests  directly 
in  the  center  of  the  pupil  of  the  deviating  eye,  when  the  observer 
notes  at  what  degree  on  the  perimeter  arc  the  light  is  resting. 
This  is  the  true  measure  of  the  deviation  in  degrees.  (See  Fig.  63). 
The  perimeter  method  is  easily  applied  in  grown  children  and 
adults,  but  is  of  little  use  in  children  under  six  years  of  age. 


Fig.  63. — Arc  measurement  of  the  deviation  in  esotropia.     The  arc  of  the  perimeter 
is  in  the  horizontal  meri(iian. 

e.  Priestley  Smith's  Tape  Measure  Method  (tangent  measure- 
ment).— In  a  darkened  room  the  observer  takes  a  position  one 
meter  from  the  seated  patient,  over  and  back  of  whose  head  is  a 
light.  The  observer  is  armed  with  a  retinoscopic  mirror  and  a 
tape  measure  marked  in  centimeters.  The  patient  gazes  at  an 
object  at  infinity.  The  light  is  thrown  by  the  mirror  on  the  deviat- 
ing eye  when  the  corneal  image  will  be  seen  near  the  limbus  of 
that  eye.  With  the  tape  measure  held  at  zero  against  the  handle 
of  the  retinoscopic  mirror,  the  observer  moves  his  disengaged 
hand  horizontally  away  from  the  direction  of  the  deviating  eye, 
directing  the  patient  to  follow  his  moving  hand  (through  which 
the  tape  measure  is  allowed  to  slide)  until  the  deviating  eye  is 


MONOCULAR    ESOTROPIA.  I75 

brought  into  such  a  straight  ahead  position  that  the  corneal  image 
rests  just  in  the  center  of  the  pupil  of  that  eye.  Then  the  obser- 
ver's moving  hand  pinches  the  tape  measure  wherever  it  may  be 
at  this  instant.  The  number  of  centimeters  the  moving  hand 
has  covered  on  the  tape  measure  records  the  number  of  degrees 
of  deviation  present.  This  method  is  quick,  accurate,  convenient 
and  quite  as  applicable  in  a  three  year  old  child  as  in  an  adult, 
f.  The  Diplopia  Test. — By  determining  the  relation  of  the 
image  of  the  squinting  eye  to  that  of  the  fixing  eye,  the  diagnosis 
of  the  actual  position  of  the  squinting  eye  and  the  degree  of  vari- 
ance of  its  visual  axis  from  parallelism  can  often  be  made.  In 
amblyopics,  the  surgeon  experiences  the  greatest  difficulty  in 
forcing  the  patient's  recognition  of  the  image  of  the  amblyopic 
eye  because,  as  has  already  been  stated,  he  never  complains  of 
diplopia,  nor  is  he  ever  conscious  of  the  false  image  of  any  object. 
Therefore,  examination  by  means  of  double  images  would  seem 
to  be  impracticable,  but  in  our  experience  persistent  efforts  have 
frequently  accomplished  the  end  sought.  At  first,  the  patient 
absolutely  refuses  to  acknowledge  the  false  image,  but  with  the 
aid  of  strong  prisms,  base  out,  before  the  squinting  eye  (bringing 
the  false  image  nearer  to  the  true)  and  by  means  of  colored  glasses 
(particularly  those  that  render  the  true  light  dull  and  indistinct) 
perseverance  will  finally  be  rewarded  with  the  acknowledgment 
that  the  object  has  its  shadow.  Having  once  secured  this  rec- 
ognition, the  subsequent  steps  present  no  difficulty.  The 
prisms,  bases  out  (and  bases  down  if  necessary),  before  the  squint- 
ing eye  which  will  fuse  the  images  will  be  the  prismatic  measure 
of  the  deviation.  By  pursuing  this  course  another  important  factor 
in  the  diagnosis,  viz.,  the  difference  of  elevation  of  the  true  and 
false  light,  is  readily  and  accurately  determined.^  The  false 
image  will  be  on  the  side  of  the  squinting  eye  (homonymous)  and 
often  below  that  of  the  true  eye.  The  lateral  deviation  equals 
20  degrees  to  40  degrees  or  more,  and  the  vertical  difference  is 
usually  overcome  by  a  prism  of  3  to  4  degrees.    This  determina- 

*  Cases  that  prove  exceptions  to  this  rule  are  those  of  false  projection  (the  so- 
called  second  fovea),  and  those  of  mental  incapacity. 


176  FUNCTIONAL  ANOMALIES. 

tion  of  hypertropia  is  necessary  to  the  treatment,  even  though 
the  result  of  the  operation  can  only  be  cosmetic.  Clinically,  we 
have  found  that  vertical  squint  is  not  transferred  with  the  lateral 
in  cases  of  high  amblyopia,  the  eyes  retaining  the  same  relative 
position  even  when  the  sound  eye  is  covered. 

g.   The  Tropometer. — While  this  is  a  supplementary  test  the 
information  furnished  by  this  instrument  is  of  value  in  indicating 

the  exact  power  of  temporal  rotation 
of  esotropic  eyes.     Its  findings  gener- 
ally show  subnormal  power  of  temporal 
remparaiio-,  7     •  rotation    m   such  cases.     The  motor 


fields  here  shown  are  from  a  typical 
case  of  monocular  esotropia  (Fig.  64). 
Another  supplementary  test  is  the 
Fig.  64.— Tropometric  fields     deviometer   of    Worth    (modified   by 

in  a  case  of  monocular  esotro-  Black),    but   it    ServeS   no   purpoSC  not 

pia  (right  eye  deviating    eye).  ^     '                                         ^    ^       ^ 

The  average  normal  rotations  fulfilled     by     the     foregoing    testS    and 

are  upward  •?6,  downward  ^2,         • ,      i.-i-  cc.  i. 

temporalward48,nasalward5o:  Simply   multiplies  office   apparatus. 

Treatment. — The  management  of 
monocular  esotropia  is  nonoperative  in  the  developmental  and 
operative  in  the  confirmed  stages. 

The  nonoperative  treatment  is  applied  with  the  hope  of  ac- 
complishing two  purposes,  namely:  the  subsidence  of  the  squint 
and  the  cure  of  the  amblyopia.  Early  in  the  history  of  the  squint 
the  peripheral  cause,  hyperopia,  can  be  set  aside  by  paralyzing 
the  accommodation,  thereby  silencing  the  abnormal  stimulus  to 
convergence  always  consequent  upon  the  unconscious  but  un- 
ceasing overaction  of  the  ciliary  muscle.  It  is  not  uncommon  to 
see  an  esotropia  disappear  in  small  children  after  two  to  three 
months  paralysis  of  the  accommodation  and  use  of  a  proper  cor- 
rection. The  drug  usually  employed  for  this  purpose,  and  the 
one  best  borne  by  children  without  serious  results  after  prolonged 
application,  is  atropin,  which  it  must  be  said  is  not  without  its 
disadvantages.  The  pupils  partake  in  the  paralysis  and  become 
widely  dilated,  giving  rise  to  photophobia;  the  follicular  glands 
of  the  conjunctiva  take  on  a  hypertrophic  inflammation,  and  the 


MONOCULAR   ESOTROPIA.  I77 

squint,  for  a  time  at  least,  seems  to  be  increased  because,  although 
the  impulse  to  accommodation  is  not  interrupted,  accommodation 
itself  (response  to  the  impulse)  is  impossible.  On  the  other  hand, 
the  associated  impulse  to  convergence  is  greater  because  of  the 
patient's  efforts  to  correct  his  defective  vision  by  calling  urgently 
on  his  ciliary  muscles.  However,  this  effect  of  atropin  is  transient 
and  may  with  safety  be  disregarded.  It  may  be  applied  either 
to  both  eyes  or  only  to  the  fixing  eye.  In  the  latter  case  induce- 
ment is  given  the  patient  to  use  the  squinting  eye,  provided  that 
its  vision  is  better  than  that  of  the  fixing  eye  when  atropinized. 
For  the  same  reason  periodic  wearing  of  a  bandage  or  screen  over 
the  sound  eye  is  advocated  to  promote  the  retinal  functions  of 
the  deviating  eye.  It  is  our  opinion  that  in  monocular  squint 
with  its  attendant  amblyopia,  this  preliminary  treatment  while 
not  often  effectual  in  curing  the  deformity  or  in  restoring  bin- 
ocular vision,  is  certainly  useful  in  preventing  an  increase  in  the 
ametropia  and  a  decrease  in  the  vision  of  the  amblyopic  eye. 
The  therapy  of  esotropia  further  includes  the  optical  correction 
of  the  refraction  error,  even  in  very  young  subjects.^ 

This  should  be  invariably  determined  by  the  ophthalmometer 
and  retinoscope  and  in  children  under  six  years  of  age  it  is  the 
part  of  wisdom  to  bind  off  one  eye  while  retinoscoping  the  other. 
No  satisfactory  treatment  of  esotropia  in  children  can  ever  be 
instituted  without  the  use  of  the  retinoscope  under  thorough 
cycloplegia.  A  full  correction,  or  as  nearly  full  as  possible, 
should  be  worn  constantly.  The  beneficial  effect  of  glasses  may 
be  increased  by  the  joint  use  of  atropin.  And  yet,  however  essen- 
tial these  means  may  be  in  the  early  treatment  of  monocular  eso- 
tropia, they  are  seldom  final,  either  singly  or  jointly.  As  long  as 
the  vision  of  the  fixing  eye  is  more  acute  than  that  of  the  squint- 
ing eye,  the  patient  will  prefer  to  use  the  better  organ,  and  neither 
the  squint  nor  the  amblyopia,  will  be  cured,  although  much  prog- 
ress in  this  direction  will  often  be  secured  by  employment  of  the 
stereoscope,  as  advocated  by  Landolt  or  the  amblyoscope  as  used 

*  Gould  has  recently  {Phila.  Med.  Jour.,  May  18,  1898)  reported  cases  in  which 
glasses  were  successfully  worn  for  squint  as  early  as  the  twenty-ninth  month  of  life. 
12 


178 


FUNCTIONAL  ANOMALIES. 


by  Worth  (see  Fig.  65)  for  education  of  the  fusion  faculty.  The 
latest  model  of  the  Worth  amblyoscope  is  arranged  with  a  double 
rheostat  so  that  the  intensity  of  illumination  in  either  tube  can  be 
perfectly  controlled  by  simply  pushing  a  steel  collar  to  and  fro. 
In  this  way  the  intensity  of  retinal  stimulation  may  be  beautifully 
equalized.  No  other  device  at  present  offers  this  advantage. 
Three  sittings  a  week  for  four  weeks  should  be  required  of  the 
patient.  If  at  the  end  of  this  time  no  improvement  is  noted 
surgical  interference  must  be  considered.  At  this  point  several 
questions  are  suggested,  viz.:  At  what  age  is  operation  to  be 
recommended?  To  what  muscles  should  the  treatment  be 
directed  ?     Should  it  include  one  or  both  eyes  ? 


Fig.  65. — Worth's  amblyoscope  with  rheostat. 

Authorities  state  that  six  years  is  the  earliest  age  at  which 
operation  ought  to  be  performed,  and  that  nine  to  ten  is  the  most 
advantageous.  The  advocates  of  early  operation  urge  that  a 
restoration  to  parallelism  of  the  visual  axes  will  prevent  the  devel- 
opment of  amblyopia,  which  they  claim  ensues  from  non-use. 
The  objections  to  early  operation  are:  the  immaturity  of  the  globes, 
the  natural  increase  in  the  power  of  the  muscles  of  growing 
children,  the  impracticability  of  accurately  estimating  the  degree 
of  the  squint,  and  hence  the  effect  desired  or  secured  by  operation; 
also  the  fact  that  when  tenotomy  of  the  internal  recti  is  performed 
crudely,  too  extensively,  or  at  too  early  an  age,  divergence  often 
ensues  between  the  twentieth  and  thirtieth  year.     In  esotropia, 


MONOCULAR   ESOTROPIA.  I  79 

as  in  esophoria,  the  surgeon  has  the  choice  of  tenotomy  of  the 
interni,  or  advancement  of  the  externi,  or  a  combination  of  both. 
Inasmuch  as  a  scientific  restoration  of  binocular  vision  cannot 
often  be  obtained  in  monocular  squint,  and  as  all  procedures  are 
carried  out  with  the  object  of  removing  the  deformity,  it  has  been 
argued  that  attention  should  be  directed  mainly  to  the  squinting 
eye.  But  tenotomy  of  the  internus  of  this  eye  only  will  be  pro- 
ductive of  little  good,  and  it  will  nearly  always  be  necessary  to 
tenotomize  the  internus  of  the  other  eye  also.  While  in  many 
instances  the  visual  axes  may  be  brought  to  parallelism  by  these 
two  operations,  it  will  often  be  accomplished  only  by  such  thorough 
division  and  separation  of  the  interni  from  the  neighboring 
tissues,  that  the  effect  is  practically  that  of  paralysis.  In  a  few 
years  the  evil  consequences  of  such  measures  crop  out  either 
in  divergence  of  the  amblyopic  eye,  or  serious  impairment  of  the 
inward  rotation  of  both  globes.  The  proceeding  that  appears  to 
offer  the  greatest  advantage,  both  immediate  and  permanent,  is 
advancement  of  the  externus  of  each  eye,  combined  with  a 
moderate  tenotomy  of  the  interni  of  the  squinting  eye.  Subse- 
quently, if  necessary,  tenotomy  of  the  internus  of  the  fixing  eye 
may  be  performed.  If  vertical  deviation  co-exist,  as  it  nearly 
always  does,  it  is  good  practice  to  divide  the  superior  rectus 
of  the  squinting  eye  first,  since  it  has  been  shown  in  many  cases 
that  when  hypertropia  has  been  eliminated  esotropia  dimin- 
ishes, and  sometimes  even  disappears. 


Alternating  Esotropia. 

Etiology. — Alternating  esotropia  differs  somewhat  from  the 
monocular  form  in  its  clinical  aspects  and  its  treatment.  For 
instance,  disease  of  the  foveal  fibers  of  the  retina  and  optic  nerve 
of  one  eye  (the  result  of  congenital  causes,  of  accidents  during  de- 
livery, possibly  of  non-use  of  the  eyes)  by  some  authorities  given 
much  prominence  in  the  development  of  the  monocular,  play 
very  little  part  in  the  alternating  form;  in  the  latter  variety, 
therefore,  amblyopia  (in  its  strict  sense)  is  not  to  be  expected. 
Moreover,  in  alternating  esotropia  the  deviation  is  perfectly  and 
readily  transferred  from  one  to  the  other  eye.  Finally,  the 
results  of  treatment,  both  in  permanently  correcting  the  deviation 
and  in  re-establishing  binocular  vision,  are  infinitely  more  favor- 
able in  this  variety.  As  to  etiology,  it  may  be  said  that  occa- 
sionally an  inherited  deficiency  or  coordination  in  the  cortical 
centers  of  fusion  is  undoubtedly  a  factor  contributing  to  the  loss 
of  binocular  fixation,  although  the  usual  exciting  cause  is  a  hypero- 
pia of  from  2. GO  to  4.00  D.  The  former  is  plainly  shown  in  the 
following  case:  E.  F.  M.,  a  seven-year-old  girl  is  brought  with 
a  history  of  esotropia  appearing  during  the  second  year  of  life. 
There  was  nothing  in  the  history  that  would  account  for  the 
deformity.  The  child  would  fix  indifferently  with  either  eye. 
The  vision  equalled  5/5  in  each  eye,  the  deviation  measure  35 
degrees,  with  both  eye-grounds  normal  in  every  respect.  Tem- 
poral rotation  in  each  eye  was  somewhat  defective.  Under 
thorough  cycloplegia  the  refractive  status  was  found  to  be  -|-  0.50 
sphere  in  each  eye.  Plainly  the  refractive  error  was  not  an 
etiologic  factor.     Investigation  showed  that  the  child's  fusion 

'  Synonyms. — Concomitant  internal  squint  or  strabismus,  alternating  internal 
squint  or  strabismus,  and  insufficiency  of  the  externi.  (It  is  to  be  hoped  that  the 
expressions  "concomitant"  and  "strabismus"  as  applied  to  esotropia,  will  soon  be 
discarded. 

180 


ALTERNATING    ESOTROPIA.  l8l 

faculty  was  practically  nil.  Fusion  training  was  tried  for  eight 
weeks,  but  without  avail  and  operation  became  the  only  resort. 
Advancement  of  each  externus  gave  a  most  satisfactory  result. 

Exceptionally,  the  degree  of  hyperopia  is  much  higher  than 
4.00  D.,  but  esotropia  is  uncommon  in  very  high  hyperopia, 
unless  the  latter  is  attended  with  congenital  disease  of  both 
fovese  (Reber).  As  in  esophoria  and  monocular  esotropia, 
the  overaction  of  the  ciliary  muscle  necessary  to  acute  vision 
stimulates  the  nucleoli  of  the  3rd  nerve,  and  through  them  the 
muscles  governed  by  the  nerve,  with  a  resultant  inward  and  up- 
ward deviation  of  either  eye  indifferently;  therefore,  the  squint 
is  transferable.  (Many  of  these  cases  conform  absolutely  to  the 
requirements  of  Bonder's  theory;  that  is,  they  are  accommodative 
esotropias). 

Diagnosis. — The  methods  employed  in  the  recognition  of 
monocular  are  equally  applicable  to  binocular  esotropia,  and 
their  detailed  description  may,  therefore,  be  omitted. 

As  has  been  said  above,  fixation  is  quite  indifferent,  and  the  slight- 
est circumstance  may  suffice  to  so  disturb  it  that  the  squint  is 
taken  up  by  the  eye  which,  up  to  that  moment,  had  been  fixing. 
It  cannot  be  too  strongly  emphasised  that  the  upward  squint  is  also 
transferred,  as  can  be  readily  demonstrated  by  testing  with 
glasses  of  different  colors.  For  instance,  with  a  red  glass  before  the 
right  eye  and  a  blue  glass  before  the  left  eye,  recognition  of  double 
images  will  be  almost  immediate.  If  the  right  be  the  fixing  eye, 
the  blue  light  (L.  eye)  will  be  to  the  left  side  of  and  below  the  red 
light.  However,  if  the  patient's  attention  is  now  directed  to  the 
blue  light,  making  it  the  fixing  eye,  the  red  light  (R.  eye)  will 
be  to  the  right  of  and  below  the  blue  one,  clearly  showing  that  each 
eye  deviated  not  only  in,  but  also  up,  when  the  other  was  fixing. 
The  lateral  deviation  varies  from  20  degrees  to  30  degrees  and 
sometimes  even  to  50  degrees,  while  the  vertical  deviation  is 
usually  corrected  by  a  prism  of  from  3  to  4  degrees.  In  conducting 
this  test,  the  surgeon  will  sometimes  have  difficulty  in  bringing  the 
patient  to  recognize  the  two  images,  but  if  diplopia  can  be  induced 
no  method  of  diagnosis  is  more  accurate.     In  children  of  suitable 


l82  FUNCTIONAL   ANOMALIES. 

age  for  operation  the  false  light  will  occasionally  be  suppressed  at 
first,  but  after  some  little  effort  it  will  be  recognized. 

It  will  thus  be  seen  that  a  description  of  esotropia  naturally  in- 
cludes a  description  of  hyperesotropia,  and  that  esotropia  as  a 
pure  lateral  deviation  rarely  exists  as  a  functional  anomaly.  The 
upward  deviation  has  been  noticed  by  few  and  overlooked  by 
many  writers,  for  the  reason  that  the  inward  turn  gives  rise  to  a 
deformity  so  great  that  it  masks  the  comparatively  insignificant 
upward  turning. 

Treatment. — As  has  been  said  in  the  treatment  of  monocular 
esotropia  it  is  not  uncommon  to  perfectly  and  permanently  cure 
this  deformity  in  small  children  even  when  alternating,  by  paralyz- 
ing the  accommodation  for  some  months  early  in  the  history  of 
the  sc[uint.  It  is  scarcely  necessary  to  add  that  the  patient  should 
wear,  from  the  earliest  possible  moment,  an  accurate  correction 
of  his  hyperopia  or  hyperopic  astigmatism.  The  act  of  binocular 
vision  is  favored  by  the  normal  bilateral  use  of  the  accommo- 
dation which  the  glasses  re-establish  and  by  the  increased  visual 
acuity  which  they  confer.  These  should  never  be  omitted,  even 
in  those  in  whom  the  deviation  seems  to  be  fixed.  Failing  in 
these  means,  resort  must  be  had  to 

Operation. — It  may  be  well  to  repeat  that  squint  is  not  pri- 
marily a  defective  muscular  condition,  and  even  less  is  it  an  affec- 
tion that  can  be  attributed  to  any  one  muscle.  It  is  a  matter  of 
convergence  power  as  related  to  divergence  power,  or  still  more 
accurately  it  is  to  be  referred  to  the  muscular  response  of  excessive 
or  deficient  nerve  stimulation.  Therefore,  it  would  seem, 
reasoning  a  priori,  that  the  remedy  is  not  to  be  found  in  opera- 
tion on  either  the  interni  or  the  externi,  but  in  regulating  or  co- 
ordinating the  stimulus  to  convergence  and  divergence  so  that 
these  functions  may  respond  relatively  equally  and  hold  the  visual 
lines  in  horizontal  equilibrium.  This  is  perfectly  true  and  is 
carried  out  in  practice,  removing — by  means  of  cycloplegics, 
convex  lenses,  muscular  and  fusion  exercises  and  the  efforts  to 
improve  vision — the  causes  of  esotropia.  But  these  measures 
often  fail  and  operative  measures  only  remain.     In  our  judgment 


ALTERNATING    ESOTROPIA. 


183 


we  have,  not  the  choice  between  tenotomy  or  advancement  when 
the  convergence  exceeds  divergence  by  20  degrees  or  more,  which 
is  always  the  case  in  functional  esotropia.  To  cut  the  interni  at 
their  insertion  so  that  an  effect  of  20  degrees  or  more  is  obtained 


Fig.  .66. — Holmes'  stereoscope. 

means  separation  from  the  sclera  not  only  of  the  tendon,  but  also 
of  all  the  subsidiary  fibers  to  the  sides  of  and  under  the  tendon. 
Such  an  extensive  operation  entails  surely  a  decided  loss  of  inward 
rotation,  a  permanent  weakening  or  loss  of  the  function  of  the 


Wy-': 

/  T 

I^^^^^^H 

L 

Fig.  67. — Bar  reading. 


muscle,"a  retrogression  of  the  caruncle  and  a  prominence  of  the 
sclera  on  the  nasal  side,  and  possibly  proptosis.  Parallelism 
of  the  visual  axes  and  the  correction  of  the  deformity  are  the 
immediate  apparently  satisfactory  results.     Later,  however,  the 


i84 


FUNCTIONAL   ANOMALIES. 


eyes  are  likely  to  diverge,  in  which  event  coordination  for  all 
distances  is  lost.  We,  therefore,  recommend  double  advancement. 
By  this  operation  the  previous  excess  of  convergence  is  neutralized 
by  the  acquisition  of  greater  divergence  so  that  by  the  use  of  the 
eyes  under  proper  conditions  (hyperopic  correction)  equilibrium  of 
the  lateral  muscles  is  secured  and  maintained.  Inward  rotation 
is  not  curtailed  and  no  fear  need  be  entertained  of  a  subsequent 
divergence.  At  the  same  time  the  grasp  and  control  of  the  whole 
cone  of  muscles  on  the  globe  is  materially  increased.     By  the 


Fig.  68. — Remy's  diploscope. 


operation  the  images  of  the  two  eyes  are  brought  closer  together 
and  the  fusion  power  is  stimulated  to  fuse  the  images.  The  opera- 
tion on  both  muscles  should  be  performed  at  the  same  sitting. 
It  may  be  necessary  in  cases  of  the  highest  grades  of  esotropia 
(internus  contraction,  internus  spasm)  to  later  tenotomize  one  or 
both  interni  in  addition  to  the  operation  of  advancement,  but  this 
step  should  be  taken  only  after  the  lapse  of  several  months,  when 
it  will  be  learned  positively  that  no  further  increase  of  divergence 
may  be  looked  for,  as  a  result  of  the  advancement.  For  some 
days,  or  even  some  weeks,  the  operator  may  be  disappointed  that 


ALTERNATING   ESOTROPIA. 


185 


the  results  are  not  all  that  he  had  hoped  for — it  is  well  known 
that  the  final  degree  of  divergence  is  not  reached  until  some  weeks 
after  the  advancement.  This  interval  should  be  utilized  to  aid 
the  development  or  the  increase  of  the  fusion  power  by  exercises 
of  various  kinds.  Indeed,  stereoscopic  exercises  with  the  Holmes 
stereoscope  are  often  of  service  both  before  and  after  operation. 
Bar  reading  after  the  operation  (see  Fig.  67)  is  much  to  be  rec- 


FiG.  69. — Bishop  Harman's  diaphragm  test.     See  also  Fig.  26. 

ommended.  The  diploscope  of  Remy  (Fig.  68)  or  Harman's 
diaphragm  apparatus  (Fig.  69)  are  both  convenient  not  only  to 
learn  whether  binocular  vision  has  been  secured  by  the  opera- 
tion, but  also  as  a  means  of  training  the  fusion  sense.  These 
same  exercises  are  of  value  in  monocular  esotropia  both  before 
and  after  operation. 


EXOTROPIA 


Exotropia  may  be 

1.  Organic,  as  a  result  of  destruction  of  the  nucleus  or  trunk 
of  the  3rd  nerve  either  from  traumatism  or  disease;  also  as  a  result 
of  direct  traumatism  to  one  of  the  internal  recti. 

2.  Partly  organic  and  partly  functional,  as  in  partial  loss  of 
vision  in  one  eye  from  anisometropia  or  antimetropia,  or  from  in- 
jury to  the  eye;  in  excessive  myopia  from  elongated  eyeballs,  in 
those  exotropias  the  result  of  too  free  tenotomies  for  esotropia 
in  childhood,  and  in  high-grade  orbital  asymmetry. 

3.  Purely  functional,  due  to  the  influence  on  a  congenitally 
w^eak  fusion  force  (desire  for  binocular  vision)  either  of  some  re- 
fraction anomaly  (usually  myopia)  or  of  the  natural  divergence 
of  the  orbital  axes  in  adult  life. 

Classes  i  and  2  may  be  binocular,  although  the  deviation  is 
usually  confined  to  one  eye. 

Class  3,  the  truly  functional  exotropias,  are  almost  always 
binocular,  and  maybe  defined  as  a  partial  loss  of  the  power  of  con- 
vergence, although  the  vision  of  both  eyes  is  alike  or  nearly  alike. 

The  organic  exotropias  (Class  i)  have  been  disposed  of  in  a  pre- 
vious chapter;  also  such  of  Class  2  as  are  mainly  organic  in  type. 
Only  those  of  the  second  class,  depending  upon  the  elongated 
eyeballs  of  excessive  myopia,  or  upon  asymmetrical  orbits,  will 
be  mentioned  here,  and  but  briefly,  the  main  question  under 
consideration  being  true  functional  exotropia. 

As  has  been  shown  in  the  previous  chapter,  esotropia  is  an  acti\e 
phenomenon  growing  directly  out  of  overaction  of  the  muscles 
under  the  domination  of  the  3rd  nerve. 

Exotropia,  on  the  other  hand,  while  due  to  an  anomalous  condi- 
tion of  the  same  group  of  muscles,  is  a  passive  phenomenon,  and 
may  in  general  terms  be  regarded  as  a  relaxation  of  all  the  muscles 

186  "~ 


EXOTROPIA.  187 

governed  by  the  3rd  nerve,  giving  rise  to  divergence  of  the  visual 
axes.  ^ 

It  commonly  affects  both  eyes  in  the  earlier  stages,  in  which  case 
it  is  known  as  bilateral,  binocular  or  alternating  exotropia.  In 
its  final  phases  it  is  usually  confined  to  one  eye,  when  it  is  known 
as  monolateral  or  monocular  exotropia. 

Etiology. — While  the  etiology  of  the  affection  sometimes  seems 
obscure,  the  fact  seems  to  stand  out  that  its  origin  is  more  or  less 
closely  bound  up  with  the  presence  or  development  of  myopia, 
which,  because  of  the  increased  length  of  the  eyeballs  and  by 
lessening  the  demands  on  accommodation  (and  hence  action  on 
the  part  of  the  ciliary  branch  of  the  3rd  nerve)  lessens  in  like 
degree  the  action  of  the  remaining  muscles  supplied  by  the  3rd 
nerve,  and  the  eyes  tend  in  the  direction  given  them  by  the 
normally  innervated  external  rectus  and  superior  oblique 
muscles —  namely,  out  and  down.  Thus  a  deviation  of  the 
visual  axes  not  only  out,  but  also  helow  the  horizontal  line  is  likely 
to  be  encountered  in  this,  the  myopic  variety  of  exotropia. 

Should  the  anomaly  be  but  a  functional  one  up  to  the  time  of 
puberty  or  soon  thereafter,  the  deviation  tendency  is  likely  to  then 
become  a  true  deviation  because  of  the  natural  divergence  of  the 
orbital  axes,  which,  as  has  been  shown  by  Weiss,  is  the  feature  in 
the  growth  of  the  adolescent  and  adult  orbit.  To  this  latter  fact, 
and  to  occasional  overaction  on  the  part  of  the  superior  oblique 
and  external  rectus  muscles,  must  be  ascribed  the  exotropia  found 
in  the  presence  of  emmetropia  and  hypermetropia. 

It  will  then  be  readily  seen  why  exotropia  is  rarely  met  with  in 
children  (save  in  high  congenital  myopes)  and  why  it  commonly 
reveals  itself  during  adolescence  or  early  in  adult  life.  Too,  the 
slow  departure  of  the  accommodation  in  the  youthful  myope, 
and  in  other  cases  the  very  gradual  increase  in  divergence  of  the 
orbital  axes,  give  to  the  approach  of  exotropia  an  insidious  form, 

'  The  condition  is  also  known  as  external  squint,  divergent  squint,  strabismus 
divergens,  concomitant  or  alternating  squint  or  strabismus,  and  insufficiency  of 
the  interni.  It  is  to  be  hoped  that  these  synonyms  will  soon  give  way  to  the 
nomenclature  here  adopted. 


105  FUNCTIONAL   ANOMALIES. 

while  esotropia,  on  the  other  hand,  is  relatively  rapid  of  develop- 
ment. Furthermore,  esotropia  in  the  child  often  becomes 
esophoria  in  the  youth  and  may  pass  through  the  various  degrees 
of  esophoria  into  muscle-balance  when  maturity  is  reached; 
whereas  exotropia  in  the  young  or  adolescent  can  only  become 
accentuated  as  the  years  wear  on.  The  natural  tendency  of 
myopic  eyes  toward  divergence  is  caused  in  part  by  the  elongated 
globes,  which  must  add  to  the  weakness  of  the  adducting  muscles 
in  all  near  work,  and  in  part  by  the  absence  of  the  impulse  to 
accommodation  to  aid  convergence.  Very  often  there  is  marked 
irregularity  or  inequality  in  vision,  and  in  some  cases  one  eye  is 
so  nearly  blind  that  it  wanders  outward  simply  in  obedience  to  the 
tendency  impressed  upon  it  by  the  outward  direction  of  the 
axis  of  the  orbit.  In  any  case  there  must  co-exist  a  lack  of 
power  of  the  adductors  to  render  the  deformity  possible,  while 
refractive  conditions  play  a  role  which  has  been  sufficiently 
explained. 

Symptoms. — The  only  noteworthy  symptoms  of  exotropia  are 
the  deviation,  the  occasional  amblyopia,  and  the  defective  vision 
consequent  upon  the  myopia  which  usually  completes  the  picture. 
The  deviation  itself  produces  no  distress  and  is  often  borne  for 
years  without  any  special  inconvenience  to  the  patient.  Rarely  is 
diplopia  present,  and  then  mainly  when  exophoria  is  passing 
over  into  exotropia.  Even  under  such  circumstances  the  patient 
is  only  occasionally  conscious  of  diplopia,  and  while  some  pa- 
tients may  be  educated  into  seeing  double  images,  in  most  in- 
stances it  is  difficult  to  excite  them. 

Amblyopia,  in  the  sense  of  the  amblyopia  of  esotropia,  is  only 
rarely  a  symptom  of  outward  deviation,  and  if  it  does  occur  it  is  a 
question  as  to  whether  it  is  of  the  same  origin  as  the  esotropic 
variety.  It  has  been  argued  that  it  grows  out  of  suppression  of 
the  image  of  the  deviating  eye,  habitually  resorted  to  by  the 
patient  to  avoid  the  confusion  of  diplopia,  and  that  if  suppression 
of  the  images  falling  upon  the  retina  of  the  unused  eye  can  be 
so  readily  learned  as  it  is  by  microscopists,  ophthalmoscopists, 
astronomers  and  others,  it  seems  reasonable  to  assume  that  it  is  re- 


EXOTROPIA.  189 

sorted  to  unconsciously,  but  none  the  less  surely,  by  exotropics 
(as  also  by  the  victims  of  longstanding  ocular  palsies  or  pareses) 
to  avert  the  confusion  of  diplopia.  We  have  no  means  of  learning 
whether  the  esotropic  infant  or  child  has  ever  seen  well  with  its 
deviating  eye  before  that  eye  deviated,  nor  whether  the  com- 
plexity of  functions  that  issue  in  binocular  vision  have  ever  been 
thoroughly  acquired  and  brought  into  harmonious  automatic 
relations.  Exotropia,  on  the  other  hand,  seldom  reveals  itself 
before  puberty — long  before  which  time  binocular  vision  has  be- 
come one  of  the  cardinal  functions  of  the  central  nervous  system. 
Let  it  be  remembered  that  the  performance  of  binocular  vision 
calls  for  harmonious  synchronous  action  on  the  part  of  areas  in  the 
motor  region  of  the  cortex,  also  on  the  part  of  a  large  portion  of 
the  occipital  cortex,  and  lastly  on  the  part  of  the  2nd,  3rd,  4th, 
and  6th  (namely  four  out  of  twelve  cranial)  nerves.  With  this 
proposition  in  mind,  it  is  not  difficult  to  conceive  that  many 
esotropic  children  have  never  thoroughly  acquired  this  complex 
function,  and  that  in  such  children  a  moderate  degree  of  hyper- 
metropia  suffices  to  so  disturb  the  act  that  the  brain  finally 
abandons  the  struggle.  Hence  we  have  spoken  of  a  congenitally 
weak  fusion-force.  Similarly  in  exotropia  (at  least  of  the  myopic 
variety),  when  the  impulse  to  accommodation  is  no  longer  excited, 
another  disturbing  factor  has  been  obtruded  on  the  act  of  single 
vision,  and  the  outward  deviation  of  the  eye  or  eyes  is  the  signal 
of  the  surrender  of  the  higher  centers.  However,  in  exotropia 
we  are  dealing  with  eyes  that  have  enjoyed  a  high  degree  of  visual 
acuity,  and  deviation  certainly  means  diplopia  with  its  sequels 
unless  one  eye  learns  to  disregard  its  images.  Necessarily  this 
has  naught  to  do  with  the  amblyopia  of  those  outward  deviations 
which  are  the  result  of  over-free  tenotomies  for  esotropia  in 
childhood,  and  which  are  to  be  regarded  more  as  pareses  of  the 
operated  interni  than  as  true  exotropias. 

It  is  proper  to  state  that  in  exotropia  there  may  be  ocular  symp- 
toms, but  these  commonly  result  from  the  refractive  error  present, 
and  generally  disappear  after  its  correction. 

Diagnosis. — The  diagnosis  of  exotropia  rests  upon  much  the 


IQO  FUNCTIONAL  ANOMALIES. 

same  methods  as  those  for  esotropia — ^namely,  inspection,  the  cover- 
test,  with  and  without  prisms,  the  study  of  the  double  images 
(when  they  can  be  induced)  with  and  without  prisms,  and  the  tape 
measure  method.  Simple  inspection  will  in  most  cases  not  only 
determine  the  presence  of  the  anomaly,  but  may  also  show  which 
is  the  fixing  eye  and  what  the  probable  degree  of  deviation. 
Resort,  however,  is  generally  to  be  had  to  the  cover-test  as  follows : 
The  patient  is  seated  facing  a  candle-flame  or  some  similar  small 
bright  object  20  or  more  feet  distant.  A  small  piece  of  card- 
board is  then  carried  from  one  eye  to  the  other  and  if  each  eye  fixes 
as  its  fellow  is  covered,  the  squint  is  of  the  alternating  variety. 
When  both  eyes  are  uncovered  it  will  be  found  that  the  patient 
consciously  or  unconsciously  uses  either  the  right  or  left  eye  by 
preference  for  fixation.  We  therefore  speak  of  it  as  the  fixing  eye. 
The  fellow  organ  then  assumes  a  varying  degree  of  divergence. 
Should  the  deviation  be  of  the  monocular  or  monolateral  variety, 
it  will  be  found,  on  applying  the  cover-test,  that  the  deviating  or 
amblyopic  eye  makes  little,  if  any,  movement  when  the  fixing  eye 
is  covered.  Alternating  exotropia  may  be  measured  with  fair 
accuracy  by  using  prisms  in  connection  with  the  cover-test. 
Having  the  patient  fix  on  the  candle-flame  or  other  object  20 
feet  distant,  a  10  degree  prism,  base  in,  is  brought  before  either 
eye,  preferably  the  fixing  one.  Applying  the  cover-test,  it  will 
be  found  that  the  excursion  of  each  eye  as  the  cover  is  shifted  from 
side  to  side  is  much  diminished,  and  by  increasing  gradually  the 
prism  strength,  base  in,  a  degree  will  finally  be  reached  at  which 
both  eyes  are  apparently  steady  as  the  cover  moves  back  and 
forth.  Not  infrequently  it  will  be  found  that  a  vertical  devia- 
tion co-exists,  when  it  will  be  necessary  to  learn  the  prism  needed 
to  arrest  the  vertical  as  well  as  the  lateral  movement.  The  prism  or 
prisms  required  to  suppress  all  movement  of  the  eyes  under  cover, 
will  be  the  prism  measurement  of  the  deviation;  and  if  in  carrying 
out  the  test,  very  high  degree  prisms  are  needed,  the  effect  can  be 
divided  between  the  eyes.  Those  not  familiar  with  the  test,  will 
do  well  to  guard  against  over-correcting  with  prisms,  as  this  will 
induce  esotropic  movement  under  the  cover  and  thus  lead  the 


EXOTROPL\.  191 

surgeon  into  serious  error.  The  test  is  purely  objective  and  of 
great  service.^ 

When  double  images  can  be  excited,  we  have  another  valuable 
test  at  hand.  By  coloring  the  image  of  the  fixing  eye  v^dth  a 
cobalt  glass,  the  relative  position  of  the  images  is  easily  studied, 
and  the  degree  of  the  prism  that  will  bring  the  images  into  a 
horizontal  or  vertical  line  (or  both)  readily  learned.  However, 
this  measure  is  applicable  only  to  those  patients  in  whom  double 
images  can  be  induced,  and  who  can  cooperate  mentally  with  the 
surgeon  in  the  study  of  the  case;  whereas,  the  cover-test,  combined 
with  prisms,  renders  the  surgeon  absolutely  independent  of  the 
patient,  and  is  of  signal  service  in  all  cases  of  alternating  exo- 
tropia  irrespective  of  age  or  mental  condition.  The  tape  measure 
method  is  applied  in  the  same  manner  for  measuring  exotropia 
and  with  the  facility  as  in  esotropia.  Moreover,  as  most  exo- 
tropics  are  adults  the  perimeter  may  be  easily  employed  for  the 
arc  measurement  of  the  deviation. 

Treatment. — The  management  of  exotropia  is  optical  and 
operative.  At  first  it  would  seem  that  treatment  might  also  be 
therapeutic;  that  if  atropin  serves  to  interrupt  the  pathologic 
process  in  the  early  stages  of  esotropia,  pilocarpin  or  eserin  ought, 
logically,  to  be  of  service  in  the  same  period  in  exotropia.  The- 
oretically, this  reasoning  is  correct,  but  unfortunately  it  is  not 
borne  out  by  clinical  facts.  In  esotropia,  we  are  dealing  with  a 
force  that  needs  curbing,  and  atropin  is  the  ideal  agent.  In  ex- 
otropia, we  have  to  do  with  functions  (accommodation  and  con- 
vergence) that  are  waning,  or  with  conditions  that  are  the  result 
of  anatomic  changes  (divergence  of  the  orbital  axes,  and  elonga- 
tion of  the  globes).  The  fact  is  that  myotics  by  stimulating  ac- 
commodation alone  would  rather  lessen  the  associated  stimulus 
to  convergence,  and  thus  add  to  the  divergence  of  the  eyes. 
Moreover,  it  would  seem  that  the  instillation  of  a  very  weak 
mydriatic  might,  by  inducing  extra  stimuli  to  the  ciliary  muscle, 
incite  the  adductors  to  action,  and  hence  be  of  service  in  the  early 

*  The  same  mistake  may  be  just  as  easily  made  in  estimating  the  prism  degree  of 
esotropia  or  right  or  left  hypertropia. 


192  FUNCTIONAL  ANOMALIES. 

Stages  of  exotropia,  although  there  is  no  record  of  such  treatment 
directed  to  early  exotropia. 

The  optical  treatment  of  exotropia  may  be  affected  by  correct- 
ing lenses  alone  or  in  combination  with  prisms.  The  greatest 
care  should  be  observed  to  learn  the  exact  static  refraction  in  every 
case,  when  the  following  rules  are  in  force  :^ 

For  non-presbyopes.  All  myopes  under  6  D.  to  be  given 
a  full  correction  of  their  optical  defect,  that  the  accommodation 
may  be  forced  into  action.  It  will  often  be  of  advantage  to  assist 
the  accommodation  at  first  with  one  drop  of  a  one  grain  to  the 
ounce  solution  of  pilocarpin  muriate  in  each  eye  three  times  a  day. 

Myopes^  of  over  6  D.  to  be  given  the  fullest  possible  correction 
consistent  with  any  degree  of  comfort  in  work  at  the  near  point. 
Pilocarpin  is  also  of  service  in  enabling  these  patients  to  become 
accustomed  to  the  new  conditions  imposed. 

Hypermetropes  of  whatever  degree  to  be  given  the  weakest 
spherical  correction  consistent  with  comfort  in  working  at  the 
near  point. 

Presbyopes  to  be  given  the  strongest  minus  spherical  (if  myopes), 
or  the  weakest  plus  spherical  (if  hyperopes)  that  will  enable  the 
patient  to  conduct  work  at  13  inches,  with  pilocarpin  (or  eserin) 
again  as  a  synergist. 

The  object  of  all  the  foregoing  measures  is  to  induce  action 
of  the  ciliary  muscle  in  the  hope  of  arousing  an  associated  stimulus 
to  the  adductors,  and  thus  lessening  the  divergence.^ 

If  eight  to  twelve  weeks'  constant  wear  of  the  correcting  lenses 
does  not  dissipate  the  exotropia,  training  of  the  convergence 
after  the  method  advised  in  the  chapter  on  exophoria  will  be  in 

'■  Refraction  under  complete  cycloplegia. 

-  In  a  twenty-year-old  young  woman  who  came  under  our  care,  wearing— lo.oo 
for  distance  and  — 6.00  for  near  work,  the  patient  was  relieved  entirelyof  her  asthen- 
opia and  incipient  exotropia  by  two  months  use  of  — 13.00  D.  S.  —  i.oo  degree  Cyl. 
180  in  each  eye  (her  full  correction),  the  employment  of  pilocarpin  as  above,  and 
training  of  the  convergence  with  prisms. 

^  It  should  be  mentioned  that  this  adaptation  of  the  correcting  lenses  to  the  exo- 
tropia applies  to  their  spherical  components  only.  Any  cylindrical  element  neces- 
sary should  be  prescribed  in  its  full  static  strength. 


EXOTROPIA.  193 

order,  bul  this  is  feasible  only  in  the  lowest  j^rades  of  exotropia 
where  binocular  vision  is  still  possible.  Anything  over  15  degrees 
falls  out  of  this  class.  As  a  last  optical  resort,  streoscopic  train- 
ing of  the  adductors  may  be  tried  after  the  method  of  Landolt, 
and  some  few  patients  will  respond  to  this  method  of  educating 
the  fusion  impulse  after  a.11  other  methods  have  failed.  Finally, 
if  after  optical  correction,  the  deviation  be  less  than  15  degrees, 
and  does  not  respond  to  convergence  training,  or  if  it  is  over 
15  degrees,  operation  is  the  final  resource.  Inasmuch  as  we  are 
dealing  with  a  passive  phenomenon,  shortening  of  the  relaxed 
muscles  is  indicated,  rather  than  tenotomy  of  their  antagonists, 
hence  advancement  is  preferred  to  tenotomy.  In  monolateral 
exotropia,  the  deviating  eye  should  always  be  approached  first. 
If  vertical  deviation  co-exist,  it  should  be  remedied  before  proceed- 
ing to  advancement  of  the  internus  of  the  squinting  eye,  and  if 
these  two  steps  leave  a  residual  deviation,  tenotomy  of  the  ex- 
ternus  of  the  squinting  eye  may  be  performed.  Any  deviation 
then  remaining  must  be  met  by  advancement  of  the  internus 
of  the  sound  eye.  Rarely  will  it  be  necessary  to  go  on  to  tenotomy 
of  the  externus  of  this  eye. 

In  binocular  exotropia,  the  muscles  to  be  attached  are  taken  up 
in  the  following  order:  Any  vertical  imbalance  must  be  first 
corrected;  efforts  to  restore  the  lateral  balance  are  then  made  by 
advancement  of  the  internus  of  the  eye  which  does  not  fix;  or,  if 
fixation  be  indifferent,  by  advancement  of  the  internus  of  that  eye 
which  presents  the  poorer  corrected  vision.  If  this  prove  in- 
sufficient, advancement  of  the  internus  of  the  fellow-eye  becomes 
necessary,  and  if  external  deviation  persists  despite  all  these 
procedures,  tenotomy  of  either  or  even  both  externi  is  in  order. 
These  latter  measures,  however,  will  be  required  only  in  the  most 
aggravated  exotropias.  In  those  few  cases  of  pure  divergence 
excess  with  fairly  well  preserved  convergence  faculty  (the  so- 
called  neuropathic  divergence),  which  usually  are  associated  with 
hypermetropic  states  of  refraction,  tenotomy  of  both  externi  may 
be  done  with  much  confidence. 

As  a  rule,  exotropes  who  have  once  possessed  the  faculty  of  bin- 


194  FUNCTIONAL   ANOMALIES. 

ocular  vision  are  much  more  easily  restored  to  its  privileges  than 
young  esotropes  who,  in  all  probability,  have  never  enjoyed 
good  binocular  vision.  Hence,  the  prognosis  of  the  operative 
treatment  of  exotropia  is  favorable,  although  the  length  of  time 
necessary  to  bring  the  visual  axes  into  coordination  extends  in 
some  cases  over  several  months.  In  those  exotropias  which  are 
the  result  of  too  free  tenotomies  for  esotropia  in  childhood,  the 
divergence  is  usually  monocular  and  is  very  wide,  frequently 
reaching  55  or  60  degrees.  In  such  cases  it  becomes  necessary  to 
do  a  wide  resection  and  advancement  of  the  internus  with  its 
overlying  conjunctiva  and  surrounding  capsule  combined  with 
tenotomy  of  the  externus  of  the  same  eye.  It  is  well  to  secure 
5  to  10  degrees  of  over-effect  in  such  cases,  as  a  portion  of  the 
effect  gained  by  operation  is  usually  lost  within  two  to  three 
months  after  the  operation. 


HYPERTROPIA 


Hypertropia,  or  true  vertical  deviation  of  one  visual  axis  above 
the  other,  is  not  often  encountered  alone,  but  is  usually  associated 
with  either  esotropia  or  exotropia  Admitting  the  relative  infre- 
quency  of  pure  uncomplicated  hypertropia,  one  cannot  but  be 
struck  with  the  meagerness  of  references  to  this  anomaly  in  the  most 
recent  as  well  as  in  the  older  text-books  on  ophthalmology;  nor 
does  recent  ophthalmic  literature  throw  much  light  on  the  sub- 
ject. And  the  foregoing  fact  is  even  more  striking  when  it  is 
remembered  that  the  same  causes  which  underlie  the  functional 
or  latent  vertical  imbalances  (hyperphorias)  lead  directly  up  to 
and  are  as  distinctly  causative  of,  the  actual  vertical  deviations 
or  hypertropias. 

Etiology. — The  ciliary  overaction  which  in  hypermetropic 
eyes  often  gives  rise  to  a  temporary  esophoria  or  hyperphoria, 
may,  under  certain  conditions,  carry  the  anomaly  from  the 
latent  or  heterophoric  class  over  into  the  actual  or  heterotropic 
phase;  in  other  words,  long  perverted  physiology  finally  issues  in 
pathology.  Just  so  long  as  the  patient's  fusion  power  asserts 
itself,  just  that  long  will  the  patient  preserve  binocular  vision  and 
in  all  likelihood  present  a  train  of  ocular  or  reflex  symptoms  as  the 
result  of  the  extra  output  of  nerve-force  necessary  tb  maintain 
fusion.  During  this  stage  deviation  tendencies  only  can  be  elicited 
— in  other  words,  we  are  dealing  with  heterophoria;  and  many 
patients  will  carry  a  defect  of  this  kind  throughout  life.  But 
it  frequently  happens  in  childhood  or  adolescence  that  the 
supply  of  nerve-force  necessary  to  fusion  is  not  equal  to 
the  demand,  and  the  muscular  system  of  one  or  the  other  eye 
gives  up  the  unequal  struggle  and  latent  tendencies  become 
manifest,  or  heterophoria  (functional  turning)  advances  now  to 
heterotropia,  or  actual  turning.  This  variety  results  in  the  vast 
majority  of  cases  either  from  uncorrected  errors  of  refraction  or 

19s 


ig6  FUNCTIONAL   ANOMALIES. 

from  the  change  in  the  dimensions  and  direction  of  the  orbital 
axes  common  to  the  time  of  puberty.  Hence,  hypertropia  is 
similar  in  origin  to  esotropia  and  in  many  respects  to  exotropia, 
with  cither  one  of  which  it  is  therefore  nearly  always  associated, 
and  upward  is  frequently  associated  with  inward  deviation  as 
seen  in  Fig.  69. 

In  hypertropia  either  the  right  or  the  left  visual  line  may  be 
habitually  higher  than  the  other  (right  and  left  constant  hyper- 
tropia respectively) ;  or  each  visual  line  may  be  alternately  higher 
than  the  other — alternating  hypertropia.  Vertical  squint  is 
further  classified  as  strabismus  sursumvergens  when  the  lower 
eye  is  the  one  that  habitually  fixes  and  strabismus  deorsumvergens 
when  the  upper  is  the  fixing  eye.  The  preceding  statements  made 
in  particular  reference  to  the  etiology  of  regular  hypertropia 
(a  deviation  of  one  visual  axis  above  the  other)  seem  to  us  none 
the  less  appHcable  to  a  certain  remarkable  class  of  cases,  mentioned 
by  Stevens,^  in  which  both  visual  axes  deviate  either  above  or 
below  the  horizontal  plane  when  the  head  and  eyes  are  in  the 
primary  position.  Deviation  of  both  axes  upward  is  termed 
anatropia.  That  is,  in  anatropia,  the  right  eye  deviates  up  behind 
the  screen  or  cover  when  the  left  is  fixing,  the  left  eye  moving  up 
also  (instead  of  down  as  in  hypertropia)  the  instant  the  cover  is 
carried  to  that  eye  and  the  right  eye  is  permitted  to  fix.  Kata- 
tropia  is  present  when  with  the  same  cover-test  the  excursion  is 
down  in  both  eyes. 

It  is  our  behef  that  anatropia  is  an  overaction  phenomenon 
and  that  in  all  probability  it  is  closely  related  to  esotropia,  a 
similar  phenomenon.  The  excessive  impulse  which  in  hyper- 
metropia  is  sent  to  the  ciHary  muscle,  affects  in  like  manner  the 
remaining  muscles  supplied  by  the  third  nerve,  in  consequence  of 
which  the  eyes  tend  in  the  direction  resulting  from  the  combined 
action  of  those  muscles,  namely,  up  and  in.  If  in  esotropia  the 
cover-test  be  used  with  the  patient  fixing  on  some  point  20  or 
more  feet  distant,  it  w^ill  be  found  that  both  eyes  deviate  not  only 
inward,  but  also  upward,  as  the  cover  is  shifted  from  one  to  the 

^Annals  d'Oculistique,  April,  1895. 


HYPERTROPIA. 


197 


Other  eye  (Fig.  yoj.  On  the  other  hand,  the  ul)sence  of  impulse  to 
the  ciliary  muscle  of  myopes  (who  commonly  use  little  if  any  accom- 
modation) carries  with  it  a  very  much  diminished  impulse  to  the 
other  muscles  governed  by  the  3rd  nerve,  and  their  resultant 
inaction  permits  the  eyes  to  be  deviated  in  the  direction  resulting 
from  the  combined  action  of  the  remaining  ocular  muscles  (the 
external  rectus  and  superior  oblique),  namely,  down  and  out. 
The  cover-test  in  such  a  case,  provided  binocular  vision  can  be 


Fin.  70. — Upward  and  inward  deviaiion  of  right  eye.  Such  upward  inward 
deviation  of  the  right  eye  is  sometimes  seen  with  congenital  paresis  or  palsy  of  the 
left  superior  rectus  with  spasm  of  the  inferior  oblique  of  the  right  eye  (the  associated 
muscle)  especially  if  the  eyes  were  carried  toward  the  left. 

maintained,  will  show  that  both  eyes  deviate  both  outward  and 
downward  under  the  cover  or  screen  as  it  is  carried  from  one  to 
the  other  eye. 

The  organic  hypertropias  (generally  paralytic),  are  seen  prin- 
cipally in  grave  cerebrospinal  disorders  and  have  been  considered 
at  some  length  in  the  chapter  devoted  to  palsies.  These  forms  of 
hypertropia  must  not  be  permitted  to  obscure  our  ideas  about 
true  right  and  left  hypertropia  and  strabismus  sursumvergens 
and  deorsumvergens,  whose  origin  is  closely  bound  up  with 
anomalies  of  refraction  and  with  the  shape  and  development  of 
the  orbits. 

The  following  case  is  in  point.  M.  B.,  a  twelve-year-old  girl, 
came  with  a  history  of  a  peculiar  appearance  about  her  right  eye 
since  her  third  year.  No  history  that  is  worth  while  obtained. 
Inspection  shows  rather  marked  facial  asymmetry.  The  right 
orbit  measured  3  mm.  less  in  the  vertical  and  transverse  diameters 
than  the  left,  also  the  right  eye  was  3  mm.  deeper  in  the  orbit 


198  FUNCTIONAL  ANOMALIES. 

than  the  left.  There  was  marked  upward  deviation 
of  the  right  eye  that  measured  16  degrees  constantly. 
At  times  esotropia  was  present,  at  other  times  it  was  not.  It 
varied  from  15  degrees  to  20  degrees.  With  the  tropometer  the 
rotations  of  both  eyes  were  as  follows:  R.  E.  Up  46  degrees. 
Down  57  degrees.  In  45  degrees.  Out  40  degrees.  L.  E.  Up 
38  degrees.  Down  48  degrees.  In  60  degrees.  Out  35  degrees. 
She  had  never  worn  glasses.     Her  refractive  status  was 

R. +  6.00  sph.+  i.oo  cyl.  90  degrees  =  5/60 
L.+   .50  sph.+   .37  cyl.  105  degrees -5/5 

which  was  ordered  for  her  when  her  esotropia  disappeared 
entirely,  the  vertical  element  remaining.  After  6  months  use 
of  the  glasses,  the  vertical  deviation  remained  at  15  degrees, 
when  tenotomy  of  the  right  superior  rectus  was  done  with  most 
gratifying  results.     Of  course  she  continues  to  wear  her  glasses. 

S5rmptoms. — The  symptoms  of  the  earliest  stages  of  hyper- 
tropia  are  largely  those  of  hyperphoria.  However,  when  the  weak 
depressors  or  elevators  have  abandoned  their  fruitless  task,  the 
eye  to  which  they  belong  will  deviate  in  the  direction  of  action  of 
the  stronger  muscles,  binocular  vision  will  be  lost  and  along  with 
it  will  most  likely  disappear  much  of  the  patient's  ocular  and 
reflex  discomfort.  The  resulting  deviation  which  is  the  main 
objective  symptom,  is  easy  of  recognition  in  most  cases,  especi- 
ally with  the  cover-test  at  20  feet.  The  cardinal  subjective  symp- 
tom is  the  amblyopia  of  the  hypertropic  eye.  In  recent  or  low- 
grade  vertical  deviations,  especially  if  they  are  alternating,  even 
corrected  vision  will  be  compromised  to  some  extent  in  both 
eyes,  although  more  decidedly  so  in  the  affected  eye.  In  old 
cases  the  fixing  eye  will  nearly  always  present  a  close  approach 
to  normal  vision  (corrected  if  necessary)  while  the  vision  of  the 
other  eye  is  often  lowered  to  a  remarkable  degree. 

The  mooted  question  as  to  whether  the  amblyopia  produces  the 
deviation  or  the  deviation  the  amblyopia  is  discussed  under  the 
chapters  on  Esotropia  and  Exotropia.  Aside  from  the  deviation 
and  the  amblyopia,  there  is  no  symptom  worthy  of  note  unless 


HYPERTROPIA.  199 

it  be  the  peculiar  ''wall-eyed"  appearance  of  such  patients, 
especially  if  the  hypertropia  be  alternating,  giving  to  the  patient 
the  well-known  hyperphoric  or  hypertropic  "stare."  Partial 
ptosis  not  ascribable  to  other  cause  is  regarded  by  some  authorities 
as  symptomatic  of  hypertropia. 

Diagnosis. — The  presence  of  this  anomaly  is  easily  detected, 
and  in  most  cases  its  character  and  the  eye  to  which  it  belongs 
can  be  determined  almost  at  a  glance.  In  the  alternating  variety 
resort  must  frequently  be  had  to  the  cover-test  to  learn  which  eye 
fixes  by  preference.  This  test  will  be  productive  of  the  best 
results  if  carried  out  in  a  half-darkened  room,  using  a  small  gas- 
flame  or  some  other  luminous  point  as  the  fixation  object.  By 
interposing  a  weak  prism  before  the  higher  eye  with  the  apex  of  the 
prism  placed  in  the  direction  in  which  the  eye  deviates,  and  in- 
creasing it  in  strength  until  the  eyes  no  longer  move  visibly  when 
the  cover  is  carried  from  one  to  the  other  eye,  the  deviation  may  be 
measured  with  a  reasonable  degree  of  accuracy.  This  method  is 
applicable  also  to  those  cases  in 
which  the  patient  cannot  be  made 
conscious  of  diplopia,  and  it  enjoys 
the  additional  advantage  of  being 
an  objective  method,  thus  rendering  ^^ 
the  surgeon  entirely  independent  of 
the  patient's  testimony.  In  cases 
that  are,  or  can  be  made,  conscious 
of  diplopia,   the  use  of  the  cobalt 

glass  before  the  sound  eye  is  of  great  value,  and  all  that  will  be 
necessary  is  to  find  a  prism  that  brings  the  two  images  to  a  hori- 
zontal level.  The  Maddox  rod  is  employed  by  some  surgeons  in 
the  diagnosis  of  hypertropia,  but  its  use  is  largely  restricted  to  the 
estimation  of  deviation  tendencies  rather  than  to  actual  deviations. 
In  all  cases  of  hypertropia,  search  should  be  made  in  the  extreme 
upper  periphery  of  the  binocular  fixation  field  for  diplopia  which 
if  found  generally  implies  paresis  of  one  or  the  other  superior 
rectus.  Thus  J.  C,  sixteen,  male,  diphtheria  six  years  ago 
following  which  the  left  eye  "took  on  a  peculiar  appearance." 


/  ; 
I. 

1 

1 

1 

200  FUNCTIONAL   ANOMALIES. 

Clinically  right  hypertropia  of  20  degrees  seemed  the  proper 
diagnosis  but  search  for  diplopia  revealed  it  most  marked  in  the 
left  upper  field  with  the  left  image  higher  (Fig.  71J.  The  tropo- 
metric  rotations  were  R.  E.  up  35  degrees,  down  50  degrees, 
nasal  55  degrees,  temporal  50  degrees.  L.  E.,  up  15  degrees, 
down  60  degrees,  nasal  50  degrees,  temporal  45  degrees.  Paresis 
of  the  left  superior  rectus  was  thus  plainly  shown  with  a  diagnosis 
of  paretic  left  hypotrop'ra.. 

Advancement  of  the  left  superior  rectus  and  tenotomy  of  the 
left  inferior  rectus  at  the  same  sitting  gave  him  approximate 
vertical  balance,  (left  hyperphoria  of  2  degrees). 

Treatment. — The  treatment  of  the  varieties  of  hypertropia 
under  consideration  is  orthoptic  and  operative. 

.By  orthoptic  treatment  is  meant  the  persistent  use  of  a  full 
cycloplegic  correction  of  any  ametropia  that  may  be  present. 
The  effect  of  such  lenses  will  frequently  be  much  enhanced  by 
continuing  the  effect  of  the  atropin  or  other 
cycloplegic  for  from  eight  to  twelve  weeks,  in  the 
hope  of  thus  re-establishing  proper  relations  be- 
tween accommodation  and  convergence. 

In  young  subjects  (under  ten  or  twelve  years) 
these  measures  will  frequently  lessen  the  devia- 
tion and  sometimes  dissipate  it  altogether. 
Tig  -2— TvDical  ^^tener,  however,  and  in  subjects  over  twelve 
left  hypertropia.  years  of  age  in  particular,  a  considerable  devia- 
tion remains,  which  must  be  met  by  some  oper- 
ative procedure  (Fig.  72).  The  laws  governing  operative 
interference  in  heterophoria  are  here  in  force.  Overaction 
hypertropias,  mainly  those  found  with  esotropia  (including 
anatropia)  demand  tenotomy  of  the  overacting  muscle  or  muscles 
of  the  higher  eye  to  be  combined  in  some  cases  with  tenotomy  of 
the  associated  muscle  or  muscles  of  the  sound  eye.  Underaction 
hypertropias  (usually  hyperexotropias  or  exceptionally  katatrop- 
ias)  will  be  best  met  by  advancement  or  muscle-shortening  of  the 
faulty  muscle  or  muscles  of  the  lower  eye,  and,  where  this  is  in- 
sufficient, by  a  similar  procedure  on  the  muscle  at  fault  in  the 


HYPERTROPIA.  201 

fellow  eye.  It  is  to  be  remembered  thai  division  of  the  superior 
rectus  acts  by  association  on  the  levator  palpebrae  superioris, 
and  is  followed,  not  only  by  depression  of  the  cornea,  but  also  by 
lifting  of  the  upper  lid,  in  consequence  of  which  a  considerable 
amount  of  sclera  will  be  exposed  above  the  cornea.  However,  this 
fact  may  be  utilized  in  cases  of  partial  ptosis,  both  to  aid  the 
elevator  of  the  lid  as  well  as  the  depressor  of  the  cornea.  It  is 
further  to  be  borne  in  mind  that  operations  on  hypertropes  over 
twelve  years  of  age  are  frequently  cosmetic  operations  pure  and 
simple;  and,  notwithstanding  Stevens'  claim  that  restoration  of 
binocular  vision  should  be  the  ultimate  aim  in  these  cases,  such 
termination  of  them  is  rare  and  must  be  viewed  only  as  a  most 
fortunate  circumstance. 

Finally,  operative  treatment  is  contra-indicated  in  hypertropia 
of  variable  degree;  or  of  recent  origin  and  progressive;  in  paretic 
cases  of  central  nervous  origin;  and  in  rheumatic  or  gouty  in- 
dividuals well  on  toward  liftv  vears  of  asre. 


PART  IV. 
OPERATIONS 


ANESTHESIA, 


In  heterophoria,  the  success  of  the  operation  depending  on  a 
partial  or  accurately  measured  tenotomy,  local  anesthesia  is 
essential.  Indeed,  a  precise  operation  cannot  be  performed  unless 
the  patient  is  conscious  and  can  advise  during  the  procedure  of  the 
effect  obtained  by  the  various  steps. 

In  heterotropia  (or  true  strabismus)  general  anesthesia  will  be 
frequently  necessary.  Operations  for  convergent  strabismus  are 
oftenest  done  on  children  under  twelve  years  of  age  and  there  are 
few  children  who  are  stoical  enough  to  bear  the  procedure  under 
local  anesthesia  whether  the  operation  be  tenotomy  or  advance- 
ment. This  is  always  a  disadvantage  in  that  the  normal  co- 
ordinations are  set  aside  by  the  general  anesthetic  and  the  eyes 
drift  outward  and  upward  into  the  position  normally  assumed 
during  sleep.  Under  these  circumstances  one  can  form  no  judg- 
ment as  to  the  amount  of  surgical  correction  necessary,  and  will 
have  to  be  guided  entirely  by  previous  experiences  as  to  how  much 
to  tenotomize,  how  much  tissue  to  remove,  or  how  far  to  advance 
a  tendon  in  a  given  case. 

In  adults  many  operations  (even  advancement)  may  be  done 
under  local  anesthesia,  especially  if  conjunctival  and  subcon- 
junctival anesthesia  are  combined. 

Ordinary  conjunctival  anesthesia  is  obtained  by  instilling  one 
or  two  drops  of  whatever  anesthetic  may  be  used  every  three 
minutes  for  five  applications.  This  will  suffice  in  all  tenotomies 
done  without  the  strabismus  hook  and  in  some  done  with  the  hook. 
In  the  latter  method,  however,  the  patient  often  complains  of 
much  discomfort  when  the  muscle  is  lifted  on  the  hook.  In- 
deed it  is  the  most  trying  period  in  the  operation.  We  have 
found  that  the  use  of  an  anesthetic   subconjunctivally  after  con- 

205 


2o6  OPERATIONS. 

junctival  anesthesia  .has  been  produced  contributes  greatly  to 
the  patient's  comfort.     The  following  solution  is  used: 

4  per  cent.  sol.  cocaine  muriate,  i  fluiddram. 
Normal  saline  solution,  i  fluiddram. 

Solution  adrenalin,  i  :  2000,  i  fluiddram. 

of  which  5  to  8  minims  are  injected  with  a  hypodermic  needle 
under  the  conjunctiva  over  the  muscle  or  muscles  to  be  attacked. 
During  the  ten  minutes  wait  for  this  solution  to  act,  gentle  con- 
tinuous pressure  is  made  on  the  eye  wth  a  gauze  pad  to  so  diffuse 
the  introduced  liquid  that  it  will  affect  the  widest  possible  area 
and  also  to  disturb  as  little  as  possible  the  natural  topography 
of  the  parts.  The  operation  may  then  be  approached  with 
fullest  confidence  and  with  a  comparatively  bloodless  field  because 
of  the  adrenalin  preparation.  In  many  adults,  if  they  have  any 
pluck  at  all,  advancements  may  be  done  almost  painlessly  by 
this  method.  The  advantage  of  having  the  patient  conscious 
with  the  normal  innervation  to  the  eye-muscles  during  such  an 
operation  cannot  be  overestimated.  Without  subconjunctival 
anesthesia,  relatively  few  advancements  can  be  performed  even 
on  the  most  phlegmatic  adults.  Naturally  other  anesthetics 
such  as  holocain  hydrochloride,  novocain,  alypin,  stovaine,  or 
beta  eucain  may  be  employed,  but  some  adrenalin  preparation 
should  be  used  with  them  whether  the  anesthesia  be  conjunctival 
or  subconjunctival.  We  have  used  beta  eucain  with  much  satis- 
faction. It  cannot  be  too  much  emphasized  however,  that  in 
children  under  twelve  to  thirteen  general  anesthesia  will  almost 
invariably  be  required. 

ANTISEPSIS.     ASEPSIS  AND  INSTRUMENTS. 

The  operator's  hands  and  nails  should  be  scrubbed  with  warm 
water  and  soap  until  all  mechanical  impediments  to  the  ac- 
tion of  the  chemical  agent  to  be  used  immediately  afterward 
are  completely  removed.  The  hands  are  then  dipped  in  a  solu- 
tion of  bichlorid,  biniodid,  or  cyanid,  of  mercury,  i  to  3000.  The 
skin  of  the  patient's  face  in  the  neighborhood  of  the  eye  is  scrubbed 


TENOTOMY.  207 

with  warm  water  and  soap,  then  douched  with  normal  salt  solu- 
tion, and  washed  finally  with  i:6ooo  mercurial  solution.  In 
this  manipulation,  particular  attention  must  be  paid  to  thorough 
cleansing  of  the  eyebrows  and  lashes.  The  conjunctival  sac  and 
the  conjunctival  surfaces  of  the  lids  are  flushed  with  physiologic 
salt  or  saturated  boric-acid  soluton,  and  fresh  cocain  solution  is 
applied.  The  instruments  are  first  placed  in  boiling  water  and 
then  in  alcohol,  where  they  are  allowed  to  remain  until  used.  This 
simple  method  of  treating  the  instruments  is  sufficiently  germicidal 
for  all  operations  where  the  field  is  not  unusually  septic. 

TENOTOMY. 

The  object  of  tenotomy  is  two-fold:  By  altering  the  tendinous 
attachment  of  a  muscle  to  change  its  mechanical  relations  to  the 
globe  and  to  the  other  muscles,  and  by  thus  lessening  the  power 
of  the  muscle  to  so  influence  the  distal  response  to  innervation, 
that  equilibrium  and  coordination  shall  be  inaugurated  or  re- 
established; second,  to  develop  or  restore  symmetric  and  corre- 
sponding nerve-excitation.  We  are  concerned,  first,  with  the 
muscle  or  muscles  at  fault,  and,  second,  with  the  degree  of  devia- 
tion— i.  e.,  whether  there  shall  be  partial  or  complete  muscle- 
division,  and  whether  it  shall  apply  to  one  or  both  eyes. 

In  heterophoria,  unless  there  is  good  ground  for  believing  that 
one  muscle  is  abnormal  either  in  structure  or  insertion, the  operation 
should  in  all  cases  be  divided  between  the  two  muscles,  relieving 
an  equal  amount  of  tension  in  each.  In  heterotropia  (esotropia 
for  instance)  the  evils  resulting  from  extensive  tenotomy  in  one 
eye  for  high  grade  deviation  are  limited  movement  nasalward, 
diplopia  in  the  periphery  of  the  field,  cicatrization  of  the  con- 
junctiva and  capsule  at  the  site  of  the  wound,  retraction  of  the 
caruncle  and  protrusion  of  the  eyeball.  In  monolateral  strabismus 
with  high  grade  amblyopia  it  is  our  practice  to  do  a  moderate 
tenotomy  of  the  internus  and  extensive  advancement  of  the 
externus  of  the  deviating  eye.  Later,  if  necessary,  advancement 
may  be  done  on  the  externus  of  the  sound  eye.     The  same 


208 


OPERATIONS. 


principles  obtain  in  exotropia,  save  that  the  muscles  to  be  attacked 
are  of  course  reversed.  In  esotropia  or  exotropia  without  well 
marked  amblyopia,  advancement  of  both  externi  or  interni  (as 
the  case  may  be)  is  the  operative  procedure  of  election. 


Fig.  73. — Instruments  used  in  tenotomy,     a,  scissors;  b  and  c,  tenotomy  hooks; 
d,  speculum;  e,  conjunctival  forceps. 

After  insertion  of  the  speculum  or  separation  of  the  lids  by  an  as- 
sistant (lid  elevator  held  in  one  hand  and  the  lower  lid  depressed 
by  a  linger  of  the  other  hand)  the  conjunctiva  and  the  capsule 
lying  immediately  over  the  insertion  of  the  tendon  into  the  sclera 
are   firmly   grasped   by   the   single   tooth   conjunctival   forceps. 


TENOTOMY. 


209 


Considerable  pressure  with  the  forceps  at  right  angles  to  the  ball 
is  necessary  to  ensure  the  embrace  of  the  capsule  with  the  mucous 
membrane.  The  advantage  of  securing  both  can  be  appreciated 
in  the  next  step,  the  incision.  If  both  structures  can  be  divided 
and  the  tendon  exposed  at  its  insertion  by  one  snip  of  the  scissors, 
this  part  of  the  operation  is  considerably  simplified.  Two  slight 
difficulties  present  themselves  in  case  the  conjunctiva  alone  has 
been  divided;  the  smooth  surface  of 
the  capsule  uncovered  by  mucous 
membrane  and  made  tense  by  out- 
ward rotation  of  the  cornea,  is  slip- 
pery and  hard  to  grasp;  and  again, 
unless  one  is  cautious  he  is  apt  to 
include  the  tendon  in  the  grasp  of 
the  forceps  and  to  divide  it  uninten- 
tionally. The  incision  should  not 
exceed  the  width  of  the  tendon;  if  the 
desired  result  is  not  obtained  it  may 
be  widened  at  the  close  of  the  opera- 
tion; if  it  be  too  narrow,  the  neces- 
sary manipulations  are  hindered  (Fig. 

74).  A  few  operators  prefer  to  make  the  direction  of  the 
incision  horizontal,  parallel  and  close  to  the  lower  border  of 
the  tendon,  but  the  common  practice,  and  the  better  one, 
is  to  make  it  vertical  in  order  that  it  may  have  the  greater 
influence  in  the  regulation  of  the  final  result.  Having  exposed 
the  tendon  at  its  attachment,  a  small  hook  is  passed  under  its 
entire  width  from  above  or  below,  the  distal  end  of  the  hook  com- 
ing into  view  at  the  upper  or  lower  extremity  of  the  incision,  using 
the  scissors  to  snip  away  any  capsular  folds  that  the  hook  is  likely 
to  push  before  it.  The  tendon  may  now  be  divided  to  any  extent 
desired  (see  Fig.  74) .  The  method  recommended  for  the  correction 
of  heterophoria  is  to  incise  first  the  middle  fibers  and  then  if 
necessary  divide  toward  the  marginal,  according  to  the  degree 
of  effect  previously  determined,  gauging  the  progress  toward 
equilibrium  by  frequent  interruptions  of  the  operations  for  exam- 
14 


Fig.  74. — Showing  size  of  verti 
cal     conjunctival    incision    also 
tendon  about  to  be  divided. 


2IO  OPERATIONS. 

ination  by  the  tests  above  described.  In  heterotropia,  the  divi- 
sion of  the  operation  into  these  stages  is  less  important  since  the 
tendon  is  to  be  detached  in  almost  its  entire  width.  If  section  of 
the  tendon  alone  vi^ill  not  restore  equilibrium,  the  conjunctival 
wound  can  be  enlarged  and  the  fibers  radiating  from  the  upper  and 
lower  margins  of  the  tendon  and  from  the  capsule  of  Tenon  can 
also  be  severed,  but  care  must  be  exercised  that  the  evil  effects  of 
too  extensive  division  of  the  capsular  attachments  already  alluded 
to  shall  be  avoided.  The  value  in  prism  degrees,  of  section  of 
the  tendon  varies  in  different  cases  from  2  to  10  degrees  or  more. 
In  graduated  tenotomy — i.  e.,  division  of  a  few  fibers  in  the  center 
of  the  tendon,  or  of  both  margins  the  effect  is  decidedly  limited 
(see  Fig.  53);  when  the  whole  tendon  is  severed,  without  addi- 
tional incisions  of  the  conjunctiva  or  capsule,  the  effect  would 
average  about  8  degrees.  In  proportion  to  the  tissues  divided  and 
the  extent  of  the  wound  the  effect  may  vary  from  slight  weakening 
of  the  muscle  to  a  practical  paralysis.  Union  of  the  tendon  to  the 
sclera  may  take  place  so  far  back  that  the  muscle  loses  all  power 
of  rotating  the  cornea,  or,  indeed,  it  may  always  remain  detached. 
Perhaps  our  figures  as  to  the  effect  secured  may  seem  small, 
but  they  are  the  result  of  an  experience  numbering  several 
hundred  tenotomies  and  they  are,  we  believe,  as  correct  as 
general  averages  usually  are. 

Tenotomy  or  advancement  of  the  superior  or  inferior  recti 
may  be  performed  after  the  same  principles  as  the  same  opera- 
tions on  the  lateral  muscles.  The  operator  should  bear  in  mind 
the  relative  less  power  of  the  vertical  than  the  horizontal  and 
consequently  confine  his  operations  within  narrower  limits. 
Since  the  defect  requiring  operation  is  proportionately  less 
(almost  one-third),  the' effect  of  complete  tenotomy  or  extensive 
advancement  or  resection,  is  almost  prohibitive  of  subsequent 
binocular  fixation  in  all  portions  of  the  field. 

Operations  on  the  oblique  muscles  are  rarely  indicated.  The 
effect  of  such  operations  may  be  more  accurately  obtained  by  opera- 
tions on  a  lateral  combined  with  an  operation  on  a  vertical  muscle. 

The  after-treatment  is  simple.     Cold  applications  for  a  few 


TENOTOMY.  211 

hours  and  frequent  instillations  of  saturated  boric-acid  solution 
are  all  that  are  necessary  in  the  majority  of  cases.  A  bandage  is 
seldom  used;  on  the  contrary,  it  may  be  positively  harmful  in 
that,  in  the  exclusion  of  binocular  fixation,  the  important  factor 
to  success,  namely,  the  unconscious  effort  at  fusion,  is  prohibited. 
If  immediately,  or  a  c^iy  or  two  after  operation,  the  defect  is 
found  to  have  been  over-corrected,  a  suture  to  either  close  the 
conjunctival  wound  or  a  deeper  one  that  shall  include  the  cap- 
sule and  the  severed  muscle  may  be  inserted.  It  is  the  practice  of 
some  operators  to  introduce  the  suture  before  cutting  the  muscle, 
so  that  an  over-defect  may  be  instantly  neutralized;  but  this  is, 
we  believe,  an  unnecessary  precaution  for  a  skilful  operator. 

Accidents. — It  occasionally  happens,  through  an  anomalous 
distribution  of  the  large  vessels,  that  one  of  them  is  torn  or  cut, 
producing  immoderate  hemorrhage.  This  is  especially  true  of 
the  vertical  muscles.  In  this  unfortunate  event  the  operation 
should  be  suspended  and  a  pressure  bandage  applied.  A  second 
accident  is  the  unexpected  perforation  of  the  sclera  by  the  scissors 
while  cutting  the  tendon,  which  must  be  ascribed  to  using  too 
sharp-pointed  scissors  or  to  cutting  with  the  ends  of  probe- 
pointed  ones  at  right  angles  to  the  tendon  (instead  of  on  a  line 
with  the  muscle),  with  undue  force.  The  operation  must  be  at 
once  discontinued,  the  conjunctiva  sutured  over  the  perforation, 
and  a  pressure  bandage  applied. 

Healing. — After  the  usual  operation,  the  tendon  re-attaches 
to  the  sclera  in  from  three  to  four  days.  If  the  wound  should 
become  infected,  tenonitis,  orbital  phlegmon,  ulceration  of  the 
sclera  or  cornea,  or  panophthalmitis  may  ensue.  Tenotomy 
has  been  known  to  be  the  exciting  cause,  also,  of  detachment  of 
the  retina,  essential  phthisis,  and  hemorrhage  fatal  to  the  sight 
and  to  the  integrity  of  the  ball. 

Disappointment  as  to  Result. — A  perfectly  performed  tenotomy 
will  sometimes  fail  to  favorably  affect  the  deviation  for  which  it  was 
undertaken,  in  which  event  it  is  not  unlikely  that  the  failure  can 
be  ascribed  to  some  anomalous  arrangement  of  the  check  liga- 
ments which  accompany  the  recti  muscles.     (See  Figs.  4,  5,  and  6.) 


ADVANCEMENT  OR  RESECTION. 


As  has  been  said  in  the  chapter  on  Tenotomy,  local  anesthesia 
(by  combined  conjunctival  and  subconjunctival  anesthesia) 
should  be  employed  whenever  feasible  in  all  advancement  or 
resection  operations.  In  children  under  fourteen,  general 
anesthesia  is  imperative  and  nothing  but  experience  will  guide 


Fig.  75. — Instruments  used  in  advancement  or  resection  operations,  a,  scissors; 
h  and  c,  strabismus  hooks;  d,  speculum;  e,  conjunctival  forceps;  /,  needle  holder; 
g.  Prince's  clamp  or  advancement  forceps. 

the  operator  under  these  circumstances  in  the  amount  of  tissue 
to  be  excised  or  the  distance  a  tendon  is  to  be  advanced. 

Numerous  operations  for  increasing  the  efficiency  of  any  one 
muscle  have  been  advocated.  Their  number  points  to  the 
inadequacy  of  any  single  procedure.     The  object  may  be  accom- 


ADVANCEMENT   OR    RESECTION. 


213 


plished  either  by  advancement  of  a  muscle  or  tendon,  or  by 
resection — or  cutting  out  of  a  piece  of  a  tendon  or  muscle.  Natu- 
rally each  of  these  methods  has  its  supporters.  It  seems  to  us 
wise  to  omit  the  description  of  the  great  majority  and  to  confine 
ourselves  to  those  which  have  proved  most  efficient  in  our  hands. 
Fig.  75  shows  the  necessary  instruments. 

The  principal  objection  to  be  urged  against  most  advancement 
operations  is,  that  the  sutures  by  which  the  advanced  tendon  is 
attached  to  the  conjunctiva  frequently  tear  out,  allowing  the 
tendon  to  recede  to  a  point  farther  back  on  the  ball  than  that  to 
which  it  was  formerly  attached,  and  the  original  deviation  is  thus 
aggravated.  The  advantage  of  resection  or  shortening  a  muscle 
is  that  there  is  no  danger  of  increasing  the  deformity  since  the 
tendon,  at  its  attachment  to  the  sclera,  is  not  disturbed  and  the 
shortening  process  is  confined  to  the  muscle  and  tendon. 

When  small  effects  are  desired  our  preference  is  for  an  opera- 
tion that  is  a  modification  of  the  tendon  folding  of  LaGleyze. 
Excepting  instances  of  marked  deformity, 
in  which  the  purpose  of  operation  is 
mainly  cosmetic,  this  measure  aft'ords 
satisfactory  results  in  many  cases.  Its 
efTect  can  be  accurately  gauged;  it  is 
absolutely  without  danger  of  increasing 
the  original  deformity;  it  is  attended 
with  but  moderate  traumatism,  and  the 
healing  is,  as  a  rule,  uneventful  and 
rapid. 

First  Step. — After  anesthetization  the 
conjunctiva  is  grasped  with  the  forceps 
over  the  inferior  corner  of  the  tendon-insertion  and  divided 
vertically  4  to  5  mm.,  and  (starting  at  the  same  point)  horizontally 
along  the  lower  border  of  the  muscle  as  far  back  as  is  necessary 
to  given  a  roomy  field  for  operation. 

The  subconjunctival  tissue  and  the  capsule  of  Tenon  are 
similarly  treated,  the  structures  thus  far  divided  forming  a  flap, 
which  is  turned  upward  (Fig.  76). 


Fig.  76. — Exposure  of 
the  muscle. 


214 


OPERATIONS. 


The  Second  Step. — The  muscle  is  now  brought  plainly  into 
view  by  the  strabismus  hook  and  freed  from  all  adhesions,  when 
a  black  silk  thread,  armed  at  each  end  with  a  fine  curved  needle, 
is  introduced  into  the  substance  of  the  muscle  from  6  to  8  mm. 
back  of  its  insertion,  one  needle  passing  through  the  upper  border 
of  the  muscle  from  its  conjunctival  to  its  scleral  surface,  the 
other  through  the  lower  border  in  like  manner,  and  the  thread 
drawn  taut  over  those  fibers  included  between  the  two  points 
of  entrance  of  the  needles. 

Third  Step. — The  needle  belonging  to  the  upper  portion  of  the 
muscle  suture  is  now  passed  under  the  tendon  at  the  upper  border 


Fig.  77. — Introduction  of  sutures. 


Fig.  78. — Tying  of  sutures,  pro- 
ducing knuckle  in  muscle. 


of  its  insertion  and  brought  out  near  the  center  of  the  con- 
junctival surface  of  the  attachment;  the  second  needle,  belonging 
to  the  lower  portion  of  the  muscle  suture,  is  introduced  in  exactly 
the  same  manner  under  the  lower  border  of  the  tendon-insertion 
and  brought  out  on  the  conjunctival  surface  just  below  the  first 
needle  (Fig.  77).  An  assistant  now  grasps  the  muscle  back  of  the 
point  where  the  needles  were  first  introduced  and  brings  the  muscle 
forward,  when  the  suture  is  drawn  tight  and  tied,  by  this  measure 
advancing  the  whole  muscle  nearly  as  far  as  the  tendinous  attach- 
ment and  producing  a  fold  or  hump  in  the  muscle  (Fig.  78). 
The  summit  of  this  muscular  fold  or  hump  is  then  cut  away, 
leaving  the  upper  and  lower  borders  intact  and  the  two  raw 


ADVANCEMENT    OR    RESECTION. 


215 


surfaces  in  juxtaposition  (Fig.  79).  The  suture  is  cut  off 
so  that  its  ends  may  protrude  a  short  distance  through  the 
conjunctival  wound,  which  is  now  brought  together  by  two 
sutures  (Fig.  80)  or  more  sutures  in  each  side. 

Pain  in  the  healing  may  be  largely  prevented  by  the  constant 
application  of  ice-water  compresses  and  frequent  instillations  of  a 
solution  of  boric  acid  and  cocain.  The  conjunctival  threads 
may  be  removed  in  a  few  days,  and  the  thread  in  the  muscle  should 
be  allowed  to  remain  as  long  as  it  causes  no  irritation.  Any 
difficulty  that  might  be  experienced  in  the  removal  of  this  deep 
thread  can  be  forestalled  by  leaving  long  ends  to  it,  so  that  it 
may  be  readily  brought  away  by  the  forceps. 


if 


Fig.  79. — Knuckle  cut  oflf  leaving 
ends  approximated. 


Fig.  80. — Finished  eiTect  after 
tj'ing  of  conjunctival  sutures. 


Capsular  Advancement. — Another  method  of  correcting  the 
smaller  deviations  is  to  advance  the  capsule  of  Tenon,  as  recom- 
mended by  de  Wecker.^  It  consists  essentially  in  incising  the 
conjunctiva  freely  in  the  vertical  meridian  about  4  to  6  mm.  from 
the  cornea;  then,  grasping  the  capsule  over  the  insertion  of  the 
muscle  at  fault,  sutures  are  made  to  take  firm  hold  on  the  capsule 
and  the  free  ends  are  carried  under  the  conjunctiva,  one  above  and 
the  other  below,  as  far  as  the  middle  of  the  cornea.  These  sutures 
are  then  tied  with  careful  attention  to  the  traction  they  produce 
on  the  advanced  capsule,  so  that  the  tension  will  be  equal  above 
and  below.     This  operation,    known  as  capsular  advancement, 

^  De  Wecker  and  Masselon,  Man.  (TOphthal.,  Vol.  II,  p.  778. 


2l6  OPERATIONS. 

is  indicated  only  in  the  smallest  degrees  of  heterophoria,  and  is  of 
no  value  in  well-established  squint. 

For  larger  and  cosmetic  effects  in  the  grosser  deviations  some 
such  operation  as  Wootten's  or  Worth's  is  our  preference. 
Worth  proceeds  by  incising  the  conjunctiva  and  capsule  verti- 
cally (Fig.  8i,  i),  and  then  bringing  the  muscle  plainly  into  view  on 
the  strabismus  hook  (Fig.  8i,  2),  when  it  is  freed  from  all  attach- 
ment for  a  distance  of  almost  8  to  10  mm.  from  its  insertion. 
At  this  point  Prince's  advancement  forceps  are  introduced  (Fig. 
81,  3)  and  made  to  clamp  between  its  blades  the  conjunctiva, 
capsule  and  muscle,  the  upper  blade  of  the  forceps  resting  on  the 
external  surface  of  the  conjunctiva,  the  lower  one  on  the  sclera. 
(It  will  thus  be  seen  that  in  this  operation  a  resection  is  done  of 
all  the  tissues  including  the  conjunctiva,  capsule  and  muscle). 
The  sutures  are  now  introduced.  Beginning  within  and  near 
the  upper  border  of  the  muscle,  a  needle  is  carried  from 
without  inward  3  to  4  mm.,  back  of  the  blade  of  the  forceps 
through  all  the  structures  (Fig.  81,  4).  On  emerging  on  the 
scleral  side  the  needle  is  immediately  reversed  in  the  needle 
holder  and  carried  back  parallel  to  the  way  it  was  brought 
forward,  but  just  above  the  upper  border  of  the  muscle,  coming 
out  through  the  capsule  and  conjunctiva  (but  not  including  the 
muscle  (Fig.  81,  5).  The  suture  is  then  tied  down  on  the  ex- 
ternal surface  of  the  conjunctiva  and  thus  secures  in  its  grasp 
a  few  fibers  of  the  muscle.  A  separate  suture  armed  again 
with  one  needle  is  introduced  similarly  at  the  lower  border 
of  the  muscle,  being  carried  in  and  out  in  the  identical  manner 
and  then  tied  (Fig.  81,  6).  The  tendon  is  now  severed  from 
its  main  attachment  and  all  line  fibrous  subsidiary  attach- 
ments dissected  away.  Turning  back  the  muscle  and  its  accom- 
panying structures  on  the  Prince's  forceps,  the  needle  belonging 
to  the  upper  suture  is  again  passed  through  all  the  structures,  being 
introduced  i  mm.  directly  back  of  the  knot  previously  made  and 
the  suture  is  carried  forward  and  anchored  firmly  at  the  original 
site  of  insertion  of  the  tendon,  care  being  taken  to  get  a  good  bite 
in  the  episcleral  tissues  with  the  needle  before  the  suture  is  drawn 


ADVANCEMENT   OR   RESECTION. 


217 


Fig.  81.— Diagrammatic  representation  of  Worth's  operation. 


2l8  OPERATIONS. 

through.  The  same  step  is  now  taken  with  the  lower  suture 
(The  object  of  bunching  up  the  muscular  fibers  in  each 
suture  as  first  tied  is  to  afford  the  traction  suture  inserted 
behind  it  something  definite  to  pull  on  without  the  danger  of 
pulling  out  through  the  muscular  fibers,  a  post-operative  ac- 
cident that  occurs  none  too  infrequently).  The  next  step  is 
to  excise  the  portion  of  the  tissues  held  in  the  grasp  of  the 
Prince's  forceps  by  cutting  with  the  scissors  between  the  forceps 
and  the  knots  adjoining  the  traction  sutures  when  quite  a  portion 
of  the  sclera  is  exposed  (Fig.  8i,  7).  The  final  step  of  the  opera- 
tion is  to  tie  firmly  together  the  two  ends  of  the  suture  aa'  and  then 
similarly  tie  down  firmly  the  two  ends  of  the  suture  hb',  which 
should  result  in  good  approximation  of  the  cut  end  of  the  muscle 
to  the  original  site  of  insertion  of  the  tendon  (Fig.  81,8).  If 
there  is  any  gaping  at  the  center  of  the  approximated  structures 
it  is  good  practice  to  introduce  a  third  suture  to  facilitate 
smooth  healing  and  afford  additional  support  to  the  previously 
introduced  traction  sutures.  It  is  difficult  to  say  in  arbitrary 
terms  just  how  much  tissue  is  to  be  excised,  but  under  ordinary 
circumstances  removal  of  a  3  mm.  wide  strip  produces  a  satis- 
factory result.  When  it  is  decided  to  do  tenotomy  and  resec- 
tion at  the  same  time  on  one  eye,  it  is  best  to  perform  the 
tenotomy  just  before  the  final  tying  is  done  with  the  advancing 
sutures  in  the  resection  operation.  This  enables  the  surgeon 
to  get  the  fullest  effect  out  of  the  resection  operation.  One 
marked  advantage  of  the  operation  just  described  is  that  all 
the  knots  are  tied  in  the  external  surface  of  the  conjunctiva,  so 
that  when  they  are  to  be  released  and  removed  no  difficulty 
whatever  is  experienced. 

When  advancement  or  resection  operations  are  done  on  one  eye 
only  {under  local  anesthesia),  the  patient  may  sometimes  be  allowed 
to  go  home  immediately  afterward  if  the  operation  has  been  done 
under  local  anesthesia.  He  should  be  cautioned  to  remain  per- 
fectly quiet  at  home  for  two  days  with  the  eye  or  eyes  bandaged. 
Any  advancement  operations  done  under  general  anesthesia 
whether  upon  one  or  both  eyes  require  that  the  patient  should 


ADVANCEMENT   OR   RESECTION. 


219 


remain  in  bed  for  forty-eight  hours  with  one  or  both  eyes  bandaged 
(as  the  case  may  be)  throughout  that  time.  If  at  the  end  of  forty- 
eight  hours  the  position  of  the  eye  is  satisfactory  to  the  surgeon 
the  bandage  should  be  reapplied  for  twenty-four  hours  longer — 
but  if  the  effect  seems  too  great  the  bandage  may  be  removed  in 
the  hope  that  the  antogonistic  muscle  may  help  to  stretch  the 
tissues  during  healing. 

Wootton's  operation  is  somewhat  similar  to  the  one  just  de- 
scribed, differing  mainly  in  the  method  of  introducing  the  sutures 
which  will  be  seen  at  a  glance  in  referring  to  Fig.  82.  There  is  the 
possibility,  however,  that  the  sutures  may  pull  forward  and  out 
through  the  fibers  of  the  muscle  in  this  operation  as  in  the  modi- 
fication of  the  LaGleyze  operation  above  described.  Valude, 
Sydney  Stephenson,  Verhoeff, 
Briggs,  Reese,  Vard  Hulen  and 
many  others  have  offered  advance- 
ment or  resection  operations  that 
differ  from  the  above  operations  in 
one  or  another  detail,  but  we  have 
found  the  one  fully  described  of  the 
greatest  service  and  to  it  we  pin  our 
faith. 

After-Treatment. — After  the 
operation  is  completed  20  per  cent, 
argyrol  solution  should  be  instilled 
and  both  eyes  bandaged,  with  the 
object  of  preventing  infection  in- 
ducing rapid  healing,  and,  by  re- 
moving any  stimulus  to  movements  of  the  eye,  prevent  tearing 
out  of  the  threads.  The  inclusion  of  the  unoperated  eye  in  the 
bandage  is  important  even  though  only  one  eye  has  been  operated 
upon,  for  by  this  means  only  will  the  eyes  be  kept  still.  Twenty- 
four  or  forty-eight  hours  later  the  bandage  may  be  removed,  the 
face  washed  with  bichloride  solution,  the  crusts  on  the  lashes 
dissolved  and  the  conjunctival  sac  washed  out  with  boric  acid 
solution.     Instillation  of  a  few  drops  of  argyrol   (20  per  cent. 


Fig.  82. 


2  20  OPERATIONS. 

solution)  is  recommended  before  the  bandage  is  reapplied.  In 
monocular  operation  the  bandage  may  be  omitted  after  forty- 
eight  hours;  in  binocular  it  should  be  continued  for  twenty- 
four  hours  longer. 

The  postoperative  reaction  usually  subsides  in  from  one  to 
two  weeks,  although  the  eyes  may  remain  congested  for  several 
weeks.  Speaking  generally,  the  sutures  may  be  removed  (under 
cocaine  anesthesia)  at  the  end  of  a  fortnight 


INDEX. 


Abducens  palsy,  diagram  of,  52 

Abduction,  100,  103,  109 

Action  of  prism  on  beam  of  light,  80 

Accommodation,  82 

Adduction,  100    103,  104,  108 

Advancement,  212  * 

after  treatment,  218,  219 

bandaging  after,  218 

capsular,  De  Wecker's,  215 

instruments  for,  212 

modification  of  La  Gleyze's  opera- 
tion, 213 

operations,  objection  to,  213 

postoperative  reaction,  220 

Wootton's  operation,  219 

Worth's  operation,  216 
Anesthesia,  205 

subconjunctival,  206 
Anesthetic  solutions,  isotonic,  206 
Anesthetics  used  in  muscular  operations, 

206 
Amblyoscope,  Worth's,  34 
AmpHtude  of  convergence,  106 
Anaphoria,  113 
Anatropia,  113,  196 
Antagonistic  muscles,  30 
Antisepsis,  206 
Arc  rotations,  109 
Asepsis,  206 

Average  arc  rotations,  21 
Axiom  concerning  prisms,  81 

Bar  reading,  38 
Binocular  vision,  23 

evolution  of,  34 

Johnson's  scheme,  35 

tests  for,  37 

Capsule  of  Tenon,  8 
Cataphoria,  113 
Catatropia,  113 
Check,  ligaments,  10 
Clinoscope,  Steven's,  112  2 
Conjugate  innervations,  30 
Conjunctival  anesthesia,  205 
Convergence,  amplitude  of,  106 

concerning,  85 

near  point,  107 


Corresponding  or  identical  points,  23 
Cortical  centers  of  the  muscles,  17, 18, 19 
Cyclophoria,  80 

Decentering  lenses,  157 

Jackson's  table  for,  158 
Diaphragm  test,  Harman's,  39 
Diplopia,  48 
Diploscope,  Remy's,  38 
Double  prism,  Maddox,  91 
Douziemeter,  161 
Duction  power,  measure  of,  103 
Ductions  or  prism  rotations,  100 

Esophoria,  79,  114 

advancement  in,  122 
convergence  repression  in,  117 
etiology,  115 
operation  in,  121 
partial  tenotomy  in,  125 
prism  exercise  in,  118 
rest  prisms  in,  119 
sedatives  in,  118 
symptoms  of,  114 
tenotomy  in,  122 
treatment  of,  117 

various  methods  of  tenotomy  in,  125 
Esotropia,  165 

alternating,  180 

advancement  in,  183 

diagnosis  of,  180 

etiology  of,  180 

operation  in,  182 

tenotomy  in,  183 

treatment  of,  182 
amblyopia  in,  171 
bar  reading  in,  183 
cover  test  in,  172 
diploscope  in,  185 
Harman's  diaphragm  test  in,  185 
due  to  congenital  paresis  of  external 

recti,  167 
etiolog}'  of,  165 
»        full  corrections  in,  177 

fusion  faculty  in,  165,  166 
monocular,  170 

advancement  in,  179 

diagnosis,  170 


221 


222 


INDEX. 


Esotropia,  measurement  of  deviation,i72 
monocular  tenotomy  in,  179 

treatment  of,  176 
perimeter  estimate  of  deviation,  173 
Priestley  Smith's  method  of  measur- 
ing, 174 
refraction  errors  and,  165 
relation  to  obstetrical  injuries,  167 

to  vertical  deviation,  179 
stereoscope  in,  183 
tape  method  measurement,  174 
tropometer  in,  176 
Worth's  amblyoscope  in,  178 
Exophoria,  79,  126 

advancement  in,  140 

amplitude  of  convergence  in,  131 

and  cycloplegics,  132 

classification,  126 

convergence  training  in,  134 

diagnosis  of,  128 

etiology  of,  127 

nerve  tonics  in,  132 

operation  in,  139 

prisms  in,  136 

prism  exercises  in,  134 

for  reading  distance,  138 
supplementary  tests,  131 

symptoms  in,  127 
tenotomy  in,  139 
treatment,  132 
Exotropia,  186 

advancement  in,  193 
classification  of,  186 
diagnosis  of,  189 
etiolog}'  of,  187 
operation  in,  193 
tenotomy  in,  193 
treatment  of,  191 
symptoms  of,  188 

Fascia,  orbital,  3 
Field  of  fixation,  binocular,  in 
monocular,  in 

Gould's  prism  battery,  100 

Hering's  test  box,  37 
Heterophoria,  75,  79 

Cobalt's  glass  test,  92 

convex  spherical  test,  93 

diagnosis  of,  88 

diplopia  or  displacement  tests,  88 

distorting  tests,  94 

etiology  of,  78 

Graefe's  diplopia  test,  89 

Maddox's  rod  test,  94 

position  of  streak  in  Maddox's  rod 
test,  95 

tests  for  the  reading  distance,  97 


Heterophoria,  the  cover  test,  96 

the  parallax  test,  96 
Heterotropia,  164 
Hyperexophoria,  79 
Hyper  kinesis,  80 
Hyperphoria,  79,  141 

diagnosis  of,  145 

due  to  central  disease,  156 

etiology  of,  144 

operation  in,  156 

optometer  in,  145 

paretic,  149 

relation  to  lateral  deviations,  150 

rest  prisms  in,  153,  154 

treatment  of,  152 

tropometer  in,  153 

spurious,  142 

statistics  of,  141 

symptoms  of,  142 
Hypertropia,  195 

advancement  in,  200 

diagnosis  of,  199 

etiology  of,  195 

operation  in,  200 

organic,  197 

symptoms  of,  198 

tenotomy  in,  200 

tropometer  in,  200 

and  esotropia,  196 
Hypoesophoria,  79 
Hypoexophoria,  79 
Hypokinesis,  80 
Hypophoria,  79 

Infraduction,  100,  103 
Innervation  of  the  muscles,  17 
Insertions  of  muscles,  7 
Instruments,  preparation  of,  207 

Jackson's  table  for  decentering,  158 

Law  of  corresponding  points,  24 

of  direction,  22 

of  projection,  21 
Lenses,  decentering  of,  157 

prismatic  testing  of,  159 
Levator  palpebrre,  7 

Maddox's   prism  test  for  reading  dis- 
tance, 98 
rod,  simple,  94 
compound,  94 
test  for  reading  distance,  98 
Muscles,  3,  4 
Muscular  balance,  76 

imbalance,  diagnosis  of,  88 
distorting  tests,  94 
Musculo-dynamics,  98,  108 


INDEX. 


223 


Nerve  supply  of  musclei,  12 
Nomenclature  of   muscular  anomalies, 

79 
Nuclear  centers,  18 
Nystagmus,  70 

Object  test  card,  Reber's,  170 
Oblique  inferior,  7 

superior,  6 
Ocular  palsies,  43 

diagnosis,  45 

etiology,  43 

oculomotor,  52 

primary  deviation,  47 

symptomatology,  46 
Operations,  201 
Ophthalmo-dynamometer,       Landolt's, 

106 
Ophthalmoplegia,  externa  chronica,  45 

interna  recurring,  55 
Orthophoria,  79 

Palsies,  conjugate,  64 
ocular,  diagnosis,  49 

diagram  of  images  in,  57,  59 
diplopia  in,  48 
electricity  in,  69 
false  projection,  47 
Maddox's  rod  in,  52 
operation  in,  70 
primar)'  deviation,  47 
prognosis  in,  66 
secondary  deviation,  47 
strychnin  in,  69 
symptomatology',  46 
treatment,  67 
vertigo  in,  48 
vicarious  rotations,  48 
Palsy,  abducens,  diagram  of,  52 
conjugate  vertical,  65 
convergence,  64 
external  rectus,  6r 
inferior  oblique,  58 

rectus,  58 
internal  rectus,  55 
recurrent  oculomotor,  53 
superior  oblique,  58 
rectus,  56 
Phorometer,  hand,  Well's,  102 

Steven's,  89 
Physiologic  diplopia,  24 
Position  of  rest,  76 
Predominant  action  of  muscles,  20 
Primar}'  posirion,  20 
Prisms,  concerning,  80 
Prism,  convergence,  100 
deorsumvergence,  100 
divergence,  100 
Measure  card,  Ziegler's,  160 


Prism,  rotations  or  ductions,  100 

sursumvergence,  100 
Prismatic  lenses,  testing  of,  159 
Ptosis,  44 

acquired,  45 

Range  of  convergence,  106 
Ratio   between   abduction   and   adduc- 
tion, 109 
Reber's  object  test  card,  170 
Rectus  externus,  5 

inferior,  6 

internus,  5 

superior,  5 
Relation  between  accommodation   and 

convergence,  82 
Resection  operations,  212 
Risley's  rotary  prism,  10 1 
Rotarj'  prism,  Risley's,  loi 
Rotation  of  the  muscles,  20 

Scheme  illustrating  accommodation  and 
convergence   at    different   dis- 
tances, 84 
associated  muscles,  28,  29 
of    the    dominant    action    of    the 

muscles,  26 
of  the  third  nerve  nucleus,  13 
Spasm  of  the  ocular  muscles,  70 
Spiral  of  insertions,  7 
Stereoscope,  Brewster's,  32 
Holmes,  33 
Javal,  33 
Wheatstone's,  32 
Supraduction,  100,  103 
Synergistic  muscles,  26 

Tenotomy,  207 

accidents  of,  2 1  r 

after  treatment,  210 

effect  gained  by,  210 

healing  after,  2 1 1 

inferior  rectus,  210 

instruments  for,  208 

partial,  210 

superior  rectus,  210 

technic  of,  207 
Theorv-  of  innervation,  19 

of  the  stereoscope,  31 
Torsion,  Maddox's  rod  in,  52 
Tropometer,  average  arc  rotations,  no 

scale  for,  in 

Steven's,  109,  no 

Vascular  supply  of  the  nerve  nuclei,  13 

of  the  muscles,  15 
Venous  supply  of  the  muscles,  16 

Ziegler's  prism  measure  card,  160 


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